What was going on when I was born?

After months of detente, the cold war between Glen Cove, L.I., and the Soviet Union heated up again yesterday. The Justice Department filed suit in Federal District Court in Brooklyn, seeking to force Glen Cove to open its beaches and tennis courts free of charge to Soviet diplomats who live on a 36-acre estate there. The dispute had been limited to angry exchanges of letters and telephone calls. The last skirmish occurred in the spring, when Mayor Alan M. Parente rejected a State Department proposal that called for the Russians to pay $4,800 to swim and play tennis and golf at municipal facilities.

Three of the nation's leading steelmakers yesterday announced increases of about 7 percent in the price of sheet and strip steel products that are used by the automobile industry and in consumer goods. The three - the United States Steel Corporation, the industry leader; No. 2 Bethlehem Steel, and the fifth- ranked Republic Steel Corporation - said the increases would take effect Sept. 1. Other producers said they were studying the action. The increase will raise the list price of cold-rolled sheet steel to $563 a ton, and zinc-coated galvanized steel to $606 a ton.

Savings banks in New York State showed considerable improvement in the second quarter, although more than half of them continued to report operating losses, according to the state banking department. Operating losses were cut dramatically, to a total of $55.1 million, from $269.9 million in the second quarter of 1982, and from $116 million in the first quarter of this year. As a result, the sense of impending doom within the industry has lifted. It has become far less likely that Federal and state regulatory authorities will force mergers of failing institutions into stronger ones.

President Francois Mitterrand said today that French troops had been sent to Chad to ''bring peace,'' but he warned that, if threatened by Libyan-backed rebels, they could go on the offensive. The President's statements, his first full exposition of policy since fighting flared in the Central African nation two months ago, appeared as a question- and-answer interview in Le Monde. The questions were not submitted in advance, but the text was personally reviewed by the President before its publication this afternoon. The interview came amid a growing public debate over France's military buildup in Chad. It also came as Paris pressed a diplomatic effort designed to avoid a clash with Libya. The commitment by France is rapidly becoming larger than any in Africa since the Algerian war two decades ago.

Burlington Northern Inc., which acquired 48 percent of the stock of the El Paso Company through a tender offer in January, yesterday offered to acquire the remaining 52 percent of the Houston-based energy concern in an exchange of cash and stock valued at $670 million. Burlington said it was offering $12 in cash, as well as newly issued preferred shares, for each of the 28 million El Paso shares it does not now own, an exchange valued at $24 a share for the El Paso stock. The railroad company's earlier acquisition of El Paso stock was also valued at $24 a share, but was paid entirely in cash.

Quotation of the Day ''Even if the Government wins this suit, the court can't force us in any way, shape or form to have the Soviets back on our beaches.'' - Mayor Alan M. Parente of Glen Cove, L.I. (A1:1.)

After 20 years growing grapes, Cloyce Pineo put a ''For Sale'' sign on his vineyard. A little way down the road, Neil Simmons hasn't gone that far, but he is thinking about it. ''I've been here 20 years and I've never seen times like these,'' Mr. Simmons said. ''We've got inflation at one end and price cuts at the other. It's devastating. I don't know any other way to put it.''

Urea formaldehyde foam insulation, which is suspected of causing cancer, respiratory distress and skin irritation, was allowed back on the market today by the Reagan Administration. An appellate court had struck down a ban on the sale of the home insulation, and the Justice Department decided not to appeal to the Supreme Court. Today's decision was a repudiation of the Consumer Product Safety Commission and prompted an angry response from its chairman, Nancy H. Steorts, whom President Reagan appointed two years ago. She Warns Consumers ''This is a problem product and one which can be very harmful to consumers,'' Mrs. Steorts said. She warned consumers that they should not be led ''to the mistaken belief that this product is now considered safe.''

Filipino dissidents in the United States may have been spied on and harassed by Philippine Government agents, according to former State Department officials and a Pentagon intelligence document. In interviews today, two former high- ranking Carter Administration officials said the United States had intercepted messages from Manila to Filipino agents in this country five years ago ordering them to harass opponents of President Ferdinand E. Marcos's Government who were in the United States. F.B.I. Investigated Matter The former State Department officials said that the intercepts were made during the Carter Administration and that the Federal Bureau of Investigation had been asked to investigate. A Defense Intelligence Agency report made public on Wednesday by Representative Don Edwards, Democrat of California, indicated that the United States believed that the practice of harassing Filipino dissidents in this country has continued.

Friday HICKSVILLE OKTOBERFEST Oompah bands will toot, Bavarian dancers will slap their soles, and lots of beer and sausages will be on hand at an Oktoberfest opening tonight and running from 7 to midnight under three tents on the football field of Holy Trinity Diocesan High School, 98 Cherry Lane in Hicksville, L. I. The performers will include Adam Barthalt and his band, the Schlierachtaler-Stamm Bavarian dance group and the Schwyzer Alplers, who produce deep tones from long Alpine horns. There will be games of chance and, for dessert, strudel, linzer tarts and cheesecake. The event continues most nights and some days through Labor Day, and a parade is scheduled Sunday. Admission: $3.50 ($1.75 for over-65's; free for under-12's with an adult). Long Island Expressway to Exit 41 south, Route 107 and then 106. Information: (516) 433-2900. HANDEL ON EAST SIDE

a sleepy-looking bunch of musicians, record-business people, managers, disk jockeys, club owners, journalists, relatives and hangers-on - club-hopping in Greenwich Village is the only way to live. And club-hopping is the basis of the second Greenwich Village Jazz Festival, which begins tonight at 5:30 with a free concert. There's probably more and better music per square foot in Greenwich Village than there is anywhere in the world. Many clubs regularly book musicians who are (or should be) internationally known, and the informality of club dates lets players take chances that they wouldn't take in a concert hall or on a record. Working steadily in a club, rather than in a one-shot concert appearance, tightens up bands as no other experience does. And since jazz musicians generally work three sets a night, close-knit Greenwich Village is perfectly laid out for anyone who'd like to catch a 9:30 set at one place and an 11:30 set a few blocks away.

Insurgents fighting the Nicaraguan Government have stepped up their activity in the last week, mounting at least eight attacks over a wide area of northern Nicaragua and inflicting scores of casualties, according to Government officials. Nicaraguan officials and diplomats say they believe that as many as 2,000 insurgents have entered Nicaragua from bases in Honduras this month. The Defense Ministry issued a statement today asserting that the country was facing ''a new escalation of aggression.'' Defense Minister Humberto Ortega told reporters over the weekend that the military situation had become ''difficult.''