What was going on when I was born?

A Congressional report identifies William J. Casey, manager of President Reagan's 1980 campaign, as the man who obtained briefing papers prepared for President Carter, Congressional sources said today. Mr. Casey, now Director of Central Intelligence, is implicated in a 2,400- page report to be released Wednesday by a House subcommittee, according to people familiar with the report. They said the year-long investigation was unable to determine who on the Carter staff had provided the documents. The subcommittee chairman urged today that an independent counsel be appointed to inquire further into the matter. A Federal judge ordered such an appointment May 14, but the Reagan Administration appealed the order, saying the judge had no legal authority to order the appointment of an independent counsel. A three judge appeals panel stayed the order indefinitely.

The Solidarity underground says it has kept a Soviet Army deserter hidden since the imposition of martial law in December 1981. The soldier said in a clandestine interview that he had been sheltered in more than 20 homes since deserting in Silesia in the fall of 1981 when the now- outlawed union's heady campaign for liberalization was at its height. ''I simply did not want to go back,'' he said, speaking nervously in a child's room decorated with Roman Catholic religious symbols. ''I did not see any future there. I used to think that maybe Solidarity would take power and on such an occasion I could stay in Poland or I could go to the West.''

In the dense, remote Peten jungle of northern Guatemala, archeologists have successfully raced the start of the rainy season to uncover a remarkable find - a painted Mayan tomb more than 1,500 years old, untouched by looters and in nearly perfect condition. As the first painted tomb to be found intact in the Mayan region since the early 1960's, it is considered by scholars to be a major discovery. Among its contents - including elaborate and mysterious wall paintings, pottery and a male skeleton wrapped in the remnants of a shroud - is a beautifully crafted jar with hieroglyphics and a screw-top lid that amazed the scientists. Arriving on the scene by jeep two hours after the discovery - at noon on May 15 - this reporter came upon a scene of intense, exhilarated activity. The euphoric mood of the archeologists - a collaborative team from the University of Texas and the Guatemalan Government - intensified later at dinner in their thatched-roof cookhouse at the campsite, when numerous toasts were offered with cans of beer.

The possibility of military aid to protect shipping in the Persian Gulf is being discussed by Washington and its allies, according to President Reagan. But, in a news conference, he said the possibility of direct American intervention was ''very slight.'' (Page A1, Column 6.) Jose Napoleon Duarte won predictions in Congress that an all-day lobbying effort would help to gain approval for $62 million in emergency military aid for El Salvador. After the Salvadoran President held a 90- minute meeting with House Democratic leaders, Speaker Thomas P. O'Neill Jr. said, ''I think the votes are there overwhelmingly.'' (A1:5.)

''I simply did not want to go back. I did not see any future there.

In a gesture that underscores a growing commitment of corporate assistance to public schools, the American Can Company yesterday conducted its annual shareholders' meeting at Martin Luther King Jr. High School on the West Side. ''Most corporate executives tend to buy off their conscience: They donate cash and walk away,'' said William S. Woodside, American Can's chairman. He told about 200 shareholders and 200 students that his company had made ''a real commitment to this school.''

Phibro-Salomon Inc., one of the nation's most prominent investment banking and commodity trading organizations, said yesterday - less than three years after the merger that formed it - that it was considering breaking up the company. In a brief statement about this surprising development, Phibro-Salomon said it was ''studying the possibility'' of selling all of its Philipp Brothers commodity trading operations, except oil, to a group of executives and employees. Phibro-Salomon emphasized that it had not yet decided whether to go ahead with the idea. It has retained Lazard Fr eres, the Wall Street investment banking firm, to study the plan.

Every business day, dozens of executives and employees in the Wall Street area enter an unmarked suite of offices in a building next to the American Stock Exchange. If they meet at the door, none of the men or women extend any sign of recognition. The unmarked suite is a clinic, and the clients - former heroin addicts - are there to obtain methadone, a synthetic opiate that blocks their desires for heroin. Uptown, in a converted tenement in the Bronx, 120 men and women begin each day chanting in unison a 200-word pledge to ''rise from the ashes'' and to reform themselves. Also former addicts, they are in a Phoenix House center that relies on therapy to overcome drug habits.

The following article is based on reporting by Anne O'Malley and Daryln Brewer and was written by Miss Brewer. A SMALL fan circulates damp air through the tightly packed rows of bodies. In the front of the room, a young man slick with sweat is lying on his back, his legs straight up in the air. Gasping for breath, he struggles to continue lifting his elbow to the opposite knee. He grunts in pain and gives up. Lee Martin screams: ''Don't stop! The results last longer than the pain.''

IT happens mostly around midday and late in the afternoon. Shoppers in food markets scoop slices of raw carrot and cucumber, shredded cabbage, canned baby corn and bamboo shoots, spinach leaves, bean sprouts, cauliflower, raisins and croutons into oblong plastic or foil containers. They are preparing lunch or dinner. Serve-yourself salad bars, featured in restaurant chains since the 1960's, have now been added to supermarkets and, more recently, to many of the small produce shops owned by Koreans. ''We have a lot of young professional people in the neighborhood and they don't like to cook after work,'' said John Lee, who installed an elaborate salad bar about five weeks ago in his store, Han's Oriental Market, 2150 Broadway, at 76th Street. ''It's convenient for them. They are not going to eat a whole broccoli so this way they can buy what they want.''

The Supreme Court, acting in a sex discrimination suit, ruled unanimously today that law firms may not discriminate on the basis of sex, race, religion or national origin in deciding which young lawyers to promote to the status of partner. In an opinion by Chief Justice Warren E. Burger, the Court said that once a law firm offers its associates the chance to become partners, the partnership decision is covered by the Federal law that prohibits discrimination in employment. The Court reinstated a discrimination suit by a woman who was rejected for partnership in an Atlanta law firm where she had worked for seven years as an associate. Under the ''up or out'' policy used by many law firms, the woman, Elizabeth A. Hishon, had to leave the firm.

The Consumer Price Index - the most widely followed inflation barometer - rose five-tenths of 1 percent in April, the biggest increase since January, the Labor Department reported today. The rise, while moderate and essentially in line with expectations, was nonetheless taken as confirming the widespread belief that the pace of inflation has picked up. Analysts noted that, unlike recent months, when price increases were concentrated in just a few sectors, last month's rises occurred virtually across the board. In the New York-northeastern New Jersey area, prices rose three-tenths of 1 percent in April, mainly because of increases in housing and transportation, but food costs fell. (Page D17.)