What was going on when I was born?

Continuing the trend of regional acquisitions by national financial organizations, Paine Webber Inc. said yesterday that it signed a letter of intent to buy the Rotan Mosle Financial Corporation, the leading regional brokerage house in the Southwest. The transaction calls for the Houston-based Rotan to receive 1,490,000 shares of Paine Webber stock, valued at about $80 million. In recent months, national financial organizations that are seeking to grow have been looking at regional brokerages. ''In my travels around the country, a number of these regional brokerages bring up the fact that they're constantly being approached,'' said Perrin Long, a securities industry analyst with Lipper Analytical Services. ''So I would think there's good competition for them.''

THERE are certain dishes I've had just once that were so good the taste of them lingered in my mind long afterward. Among these are two Korean specialties that were first prepared for me years ago in Seoul. Their names, when transliterated, are sin-sul-lo and koochul-paan. They're rather elaborate dishes that are traditionally served for special events. Koo-chul-paan is an appetizer. The word literally means nine-hole or nine-section dish, which refers to the way it is usually served - in a lacquered octagonal container resembling a wooden candy box with a lid. When the lid is lifted, there is a center section in which small, round, thin pancakes are stacked. Around the center are eight receptacles that hold various savory, finely shredded foods to be added to each pancake before folding, dipping into a mustard-soy sauce and eating. The fillings can vary from table to table but normally include such things as shredded beef, mushrooms, carrots and cucumbers.

Lech Walesa was questioned by the police today, the third time in less than a week, amid indications of official concern over a call by underground leaders of Solidarity for demonstrations on May 1. A joint statement by the Communist Party's Politburo and the Government warned of a ''desperate adventurist attempt to incite incidents that have not happened for a long time.'' Calling for a ''responsible attitude,'' the statement said such acts could ''cast a shadow'' over preperations for the visit of Pope John Paul II in June. ''Society can count on the institutions of order,'' the statement said. Mr. Walesa has been defying the authorities by announcing last week that he met with the Solidarity underground leaders, who have called for the May Day demonstrations, and by saying that he intends to do so again.

Mayor Koch, saying he was disappointed by the low number of black and Hispanic people hired by some city agencies, prohibited his commissioners yesterday from filling most jobs that pay $20,000 or more a year until he had time to recommend applicants. In response to questions, Mr. Koch said his action was in part motivated by criticism that he has been insensitive to black and Hispanic New Yorkers. Such charges have been frequent since Mr. Koch took office in 1978, most recently over his successful backing of Deputy Mayor Robert F. Wagner Jr. as the city's next Schools Chancellor. ''It is a consideration,'' the Mayor said in describing the relationship between his order and the criticism over Mr. Wagner's selection as Chancellor. ''It is not the consideration.''

The bodies of two teen-age girls were unearthed on Staten Island yesterday, and the authorities linked their deaths and those of three other people to a man who served 16 years in prison for the murder of a municipal prosecutor in New Jersey. The suspect, Richard F. Biegenwald, 42 years old, was paroled in 1975. He was arrested three months ago in one of the killings, that of a young woman in Asbury Park, N.J., last August, and is being held in Trenton State Prison. The girls' bodies were discovered in the rural Charleston section of Staten Island. The bodies, one mutilated and both wrapped in green plastic bags, were lifted from under 30 inches of mud next to a small frame house that was occasionally occupied by Mr. Biegenwald.

A wintry spring storm yesterday unloaded up to 15 inches of snow on parts of New Jersey and nine inches on Albany, forced 10 school districts in Westchester County to close and knotted traffic throughout the metropolitan area. ''I kind of expected to be transplanting day lilies today,'' said Spencer Eckel of Norfolk, in northwestern Connecticut. ''I guess I'll just shovel more snow.'' Yesterday the town got its second major snowfall in four days - seven inches - and then saw rain turn it into a rug of slush. ''I was in Baltimore the other day, and the daffodils were out, the sun was up, the lawns were mowed,'' Polly Millard said. ''I came home to this.''

Twenty utilities in Washington State, Idaho, Oregon and Montana, which together owe about half of the $7 billion debt on two canceled nuclear power plants, agreed today to pay their accumulated debt into court-administered reserve accounts. It was unclear how many others among the 65 participants billed 11 days ago by the Washington Public Power Supply System also would put funds into the temporary accounts. A spokesman for the supply system said that two smaller utilities, accounting for 2.8 percent of the debt, refused to make the payments. Payments Into Accounts Judge H. Joseph Coleman of the King County Superior Court ruled on Monday that the utilities could pay into the accounts until justices on the Washington State Supreme Court decided whether the utilities were liable for the debts.

International Rescue workers pulled more bodies from the rubble of the American Embassy in Beirut, but said that many other Americans and Lebanese were still buried under layers of concete and were presumed dead. The state-run Beirut radio said the death toll from Monday's explosion had reached 40. An Embassy spokesman said the bodies of 8 Americans had been removed from the rubble and that 8 other Americans and 20 Lebanese were missing. (Page A1, Cols. 4-5.) Key Congressional panels reacted to the bombing of the American Embassy in Beirut by moving to force the Reagan Administration to seek Congressional approval for any widening of the role of the United States Marines in Lebanon. (A8:3-6.)

Rescue workers pulled more bodies from the rubble of the United States Embassy in Beirut today, but they said many other Americans and Lebanese were still buried under layers of concrete and were presumed dead. Lebanese civil defense experts and Red Cross volunteers, working with cranes and bulldozers, dug through the ruins of the embassy around the clock in a desperate search for any survivors of Monday's bomb attack. By this evening, the state-run Beirut radio reported that the death toll from the explosion had reached 40, including American and Lebanese members of the embassy staff as well as Lebanese visitors and passers-by. Bodies of Americans Removed According to an embassy spokesman, the bodies of 8 American citizens have been removed. An additional 8 Americans known to have been in the building, as well as 20 Lebanese and 1 other person, are still unaccounted for. American officials said all of the missing are believed to be dead and buried in the debris.

Senate Republicans reached a compromise agreement tonight to postpone for four years, and perhaps indefinitely, the withholding of taxes from interest and dividend income. C. Anson Franklin, a White House spokesman, gave the compromise a cool reception. He said the White House had not struck any deal and had not changed its position. The White House opposes repeal of the withholding law, which is to become effective July 1.

The Koch administration announced yesterday that it was offering to sell 67 city-owned commercial buildings on shopping thoroughfares in depressed residential neighborhoods. The prices for the vacant buildings range from $12,000 to $40,000, and the city is promising qualified buyers purchase and renovation loans at below-market rates, the Mayor said. The offer, Mayor Koch explained at a City Hall news conference, is part of the city's two-year-old ''shopsteading'' program. The buildings, including 25 on 125th and 135th Streets in Harlem and 17 on Fifth Avenue in Brooklyn, are in all five boroughs. They range from small, two-story buildings to a five-story loft building.

The Federal Highway Administration, under legal challenge from four states because of its orders to admit double-trailer trucks to many principal Federal highways, today allowed those states to cut back the routes the trucks can use. Altogether, the Federal agency has designated a network of more than 180,000 miles of federally assisted highway as open to the double rigs. New York, New Jersey and Connecticut are among a dozen states that have raised safety objections to the proposed Federal network but have not taken legal action. The law in dispute, signed in January, mandates that the states allow the big rigs on the 42,000-mile nationwide Interstate Highway System and permits the double trailers on other designated highways. The law also increased motor fuel taxes and truck fees.