What was going on when I was born?

The nation's rental car industry, benefiting from an upturn in air travel and an increase in demand for the used cars it sells to the public, is apparently recovering after two stagnant years. The turnaround was reflected this week in the announcement by the RCA Corporation, owner of the Hertz Corporation, that it was ending its 18- month effort to sell the nation's largest rental car company. ''We began seeing an upturn in January, and I expect the business to continue getting better throughout the year,'' said Frank A. Olson, the Hertz chairman, in an interview yesterday. Hertz has about 38 percent of the rental car market.

New York City yesterday pulled out of an agreement with the state's Urban Development Corporation to redevelop Times Square and said it would complete the $1 billion plan itself. Mayor Koch announced the withdrawal in a statement read by the chairman of the City Planning Commission, Herbert J. Sturz, at a board meeting of the Times Square Redevelopment Corporation. The Times Square agency is made up of two members appointed by the city, including Mr. Sturz, and three by the U.D.C., including its chairman and president, William J. Stern.

Because of an editing error, an article yesterday about the decision of the A.F.L.-C.I.O. executive council to advance the date of the labor federation's Presidential endorsement incorrectly described the procedure. The federation's general board is to recommend a candidate to the convention.

THE heart starts to pound, the upper lip trembles, the mouth dries out, the eyes blur, the butterflies start fluttering in the stomach. Many people know the meaning of these symptoms: It is time to give a public speech. Until recently, it was usually men who suffered in this manner. But now that more women have jobs that frequently require them to do public speaking, they, too, are having to cope with the stage fright and nerves that have made it so feared. Speech experts often quote a survey taken in 1973, in which 3,000 Americans were asked: ''What are you most afraid of?'' Their most frequent reply: ''Speaking before a group.'' It was mentioned more often than death, illness and financial problems. According to the experts, the fear of being humiliated and the fear that others will ''see the real person underneath'' are the major causes of difficulty.

A raging underground electrical fire in midtown Manhattan yesterday plunged the garment center and the city's busy Herald Square commercial district into a chaotic, extended power failure. The blackout struck an area of 12 square blocks - from 30th to 42d Street between the Avenue of the Americas and Seventh Avenue. It closed hundreds of offices and businesses, including Macy's and Gimbels, clogged traffic in much of midtown, knocked out thousands of telephones and disrupted countless lives. At 5:37 P.M., 16 hours after flames erupted in a subterranean power station that had been flooded by a water-main break, firefighters brought the blaze under control. Major Losses Feared But officials of the Consolidated Edison Company said heavy damage to electrical equipment in the fire-ravaged vault under Seventh Avenue and 38th Street made it unlikely that all power would be restored to the area before Monday. Efforts to make emergency hookups to three other power substations in Manhattan were expected to begin today.

An article in Business Day yesterday on the RCA Corporation's decision against selling its Hertz car rental subsidiary was incomplete in some editions. A supplementary article appears today on page D1.

The rest of the world is awash in oil these days, and there's an awful lot of dried fish here to prove it. The 16,000 or so metric tons of dried fish are out of view, stored in hundreds of warehouses up and down the rugged coastline. But no one here has any trouble seeing their link with the oil glut. It is a link that connects Norway with, of all places, Nigeria. By last year, the combination of recession, energy efficiency, and high levels of oil production had sapped the industrial world's appetite for the high-priced crude oil of Nigeria and other members of the Organization of Petroleum Exporting Countries.

The largest garment manufacturing center in the world found itself in disorder and darkness yesterday, faced with millions of dollars in possible losses during one of its most critical sales weeks of the year. This is market week, when most out- of-town buyers come to New York to order next year's resort and early spring lines from women's clothing manufacturers. There could hardly have been a worse time for a large portion of the garment district to be crippled by the water-main break, transformer fire and subsequent blackout. Half of Companies Affected At least half of the manufacturing, marketing and designing companies packed into the always chaotic piece of midtown that is the garment center were affected by the power failure.

''I'D like to do a whole skyscraper of sandblasted glass,'' says the New York architect Steven Hall. ''It has enormous potential.'' The decorative ''etched'' glass that was so popular in the 1920's and 1930's has, over the last decade, been making a dramatic reappearance in buildings, from commercial structures, to restaurants, to houses and apartments. Designers and architects are using the glass as room dividers, fire screens, windows, table tops and doors. They are frosting glass lightly, carving it deeply, carving on both sides, inlaying it with metals, drawing realistic figures, and creating abstract compositions. Some of the work is in the Art Deco tradition of oblique, dynamic, geometric designs; some of it is almost atmospheric, with a hazy mood of fantasy, the softly delineated scenes representing distant times and places.

Stock prices rebounded moderately yesterday following their recent sharp declines, buoyed mainly by bargain-hunting in many of the recently depressed issues. The Dow Jones industrial average ended the session up 7.71 points, to 1,175.98. In the previous nine sessions, the key barometer dropped more than 70 points because of investor fears over rising interest rates and concern that the trend would continue over the near term. In the overall market yesterday, advancing issues on the New York Stock Exchange outnumbered stocks that fell by 992 to 584. Turnover on the Big Board expanded to 82.9 million shares from 81.4 million shares on Tuesday as institutional interest again increased.

At Camp Isabella Freedman, the campers swim, row boats and make potholders. They whisper in their cabins after ''lights out'' and they start summer romances. And sometimes they write letters to their grandchildren. ''My daughter told me, 'Behave yourself and make sure your name is on your bloomers,' '' said Evelyn Cohen, who is 71 years old.

The Economy Retail sales slipped a bit in July after registering gains for the last four months, the Commerce Department reported. In the .03 percent decline, it said, increases for food, furniture and appliance stores were offset by declines for autos, building materials and general merchandise stores. (Page D1.) In New York City, sales at seven major department stores rose an average 2.6 percent, after a strong surge in June. (D3.) The Federal Reserve authorized bank holding companies to offer brokerage services, thus further narrowing the gap between the banking and securities industries. The Fed also cleared the acquisition by Chase Manhattan of Rose & Company Investment Brokers of Chicago. (D1.)