What was going on when I was born?

A Weather Underground fugitive who had been sought for two years in the $1.6 million Brink's robbery and murder case has been arrested in New Jersey by a police officer who became suspicious of her ill-fitting wig. New Jersey police officials identified the suspect as Susan Lisa Rosenberg, who also was sought on Federal charges that she aided the 1979 prison escape of Joanne Chesimard, a Black Liberation Army leader. Miss Rosenberg, 29 years old, and a companion, Timothy A. Blunk, 27, were arrested Thursday night in Cherry Hill, near Philadelphia. The police said the couple had stopped their car on Berlin Road, off Interstate 295, to unload 740 pounds of dynamite and weapons, including a submachine gun, into a rented roadside storage locker.

Middle- income residents of New York State who own property and itemize their deductions would owe much higher taxes under the Treasury Department's tax proposals than they do now, according to a preliminary analysis by an experienced accountant. For example, a family living in New York City with an annual income of $25,000 and typical deductions would owe 23 percent more in taxes under the Treasury plan, announced Tuesday. A family living in a suburb in New York State and working in the city with an income of $50,000 would owe 54 percent more. Both families were assumed to own their homes. The analysis showed, however, that New York State residents earning $25,000 and less who take the standard deduction would save considerably under the Treasury's plan and that a family with an income of $100,000 and typical deductions would have to pay approximately the same taxes as it now pays.

Donald J. Trump said yesterday that he had an agreement to buy the site of the proposed $1 billion Lincoln West housing and office complex on the West Side and that he planned to redesign the project. Mr. Trump, the 38-year-old developer of Trump Tower and the Grand Hyatt Hotel, among other projects, and the owners of the site said the sale price would be $95 million. Mr. Trump said he hoped to renegotiate a $100 million package of public amenities that the original developers had agreed to provide to the city and to change the name of the project. 'A Job Everyone Wants' ''My attitude is that I expect to work with the community,'' Mr. Trump said. ''What we want to do is a job everyone wants. The job they proposed was a job everyone didn't want.''

President Reagan tentatively decided today on cuts in the projected budgets for Medicaid and Federal housing assistance, according to Administration officials. He is also leaning toward a freeze on Federal salaries and on cost- of-living adjustments for all pension programs but Social Security, they said. The officials described the President as going through a slow and difficult process of making his initial, tentative decisions on a new budget while attempting to hold overall spending next year at this year's level. The White House staff has used the term freeze, but officials said the term was more useful politically than technically.

Capping a 22-year effort, representatives of nine major Protestant denominations yesterday approved a set of accords intended to provide the theological basis for the eventual merger of the churches. The Consultation on Church Union, meeting in Baltimore, resoundingly adopted a 48,000-word statement of agreement on key issues, including baptism, forms of ministry, creeds and worship. Although conceptual rather than practical, church officials say it helps remove the big theological roadblocks that have retarded unity. ''Division in the life of the church is a contradiction of its very nature,'' the statement says. ''The reasons for seeking unity among the churches are found in the Bible, in tradition and in the imperatives of witness and worldwide mission.''

Doctors twice today temporarily switched William J. Schroeder to an 11-pound power source from the 323-pound machine that had been powering the plastic-and-metal pump in his chest. The successful experiments could pave the way for a reasonably comfortable life for recipients of artificial hearts. The most tense moments of the experiments came when the doctors turned off Mr. Schroeder's artificial heart entirely for a few beats as they took about about three seconds to change the air hoses from one power source to the other. The small power source, the Heimes portable driver, powered Mr. Schroeder's heart successfully for periods of 22 minutes this afternoon and an hour tonight.

The Pentagon ordered the nuclear-powered aircraft carrier Nimitz to the Cuban coast today to assist a Navy-chartered vessel that had broken down and drifted into Cuban waters. The vessel, the 105-foot Seaward Explorer, and its five-man crew were eventually rescued by a United States Coast Guard cutter after a Cuban Navy patrol boat tried to take it under tow, Coast Guard officials in Miami said. Pentagon officials said that they were not certain what the Seaward Explorer was doing before its engine broke down, but that they believed it was involved in oceanographic research.

As a boy, Ivan Guzman de Rojas would roam among the alpaca herds and mud huts of the high Andes with his father, at the time Bolivia's best-known painter of the Indians known as the Aymaras. ''My father would tell me, this is a rich culture,'' Mr. Guzman recalled of the Aymaras. ''Don't be fooled just because its appearance is poor.'' Now, 40 years later, Mr. Guzman says he has made discoveries that support his father's claim, although in an entirely unexpected way. He has concluded that the ancient Aymara language is an ideal tool for the computer.

Zambia, a landlocked country in south-central Africa that is now in its third year of drought, could be a substantial food exporter. Instead, this nation of 6.5 million people has been spending its critically short foreign-exchange earnings for food imports even in good years. Now, afflicted by the same catastrophic drought that has hit Ethiopia, Chad and Mozambique and threatens millions of people in more than 20 other African nations, Zambia is staving off famine only through the tens of thousands of tons of food brought in by international relief shipments. The problem here is not simply drought and desert expansion, brought about by weather and by human misuse of the land. The problem is insufficient food production.

Salvadoran rebel representatives offered Government officials a three-stage peace plan today that calls for the eventual formation of a new government, a new constitution and reorganization of the armed forces. In the past, the Government has rejected all the major components of the plan. But senior rebel officials, reached by telephone in Mexico and Costa Rica, said that their proposal was intended as a starting point for further talks and that it had been approved by the leaders of both the rebels' political wing, the Democratic Revolutionary Front, and their military organization, the Farabundo Marti National Liberation Front. The proposal was made as both sides met in El Salvador for the second time in a full day of talks aimed at finding ways to end the five-year-old civil war.

Tanks and armored vehicles that were deployed around Managua earlier this month have been removed, a survey of the city indicates.

East German border guards today removed the last of some 60,000 shrapnel devices from the heavily guarded fenced frontier with West Germany, the Interior Ministry said. The removal of the SM-70 firing devices, which detonated on contact to deter East Germans from fleeing across the frontier, fulfilled a pledge by Erich Honecker, the East German leader, after Bonn provided a $496 million loan in the summer of 1983.