What was going on when I was born?

The Reagan Administration plans to issue a white paper describing an arms buildup in Nicaragua in an extensive new campaign to persuade Congress to renew aid to Nicaraguan rebels, senior Administration officials said today. Despite repeated votes in recent years by the House against aiding the rebels, the Administration believes it has a chance of gaining approval for such aid in March or April because of growing opposition in Congress to the Nicaraguan Government and its ties to Cuba and the Soviet Union. Details Are Not Final Although detailed plans for the lobbying effort are not final, the officials said, it will include publication later this month of a report on a military buildup in Nicaragua and efforts by Government officials to focus public and Congressional attention on Soviet arms shipments to Nicaragua. United States aid to the rebels, which was funneled through the Central Intelligence Agency starting in 1981, ran out in September. Since then the rebels have financed their operations with private donations and with money and arms provided by governments, including Israel's, according to rebel leaders and Administration officials.

In a surprise jolt to the seniority system, House Democrats defied their leaders today and ousted 80-year-old Representative Melvin Price as chairman of the Armed Services Committee. In his place they chose Representative Les Aspin of Wisconsin, a relatively junior member of the panel who has been a sharp critic of Pentagon policies. The dramatic move means House Democrats are likely to take a more combative attitude toward President Reagan's military policies, demanding greater cuts in Pentagon spending and more serious efforts to reach arms control agreements with the Soviet Union. Impatience and Frustration The vote also points up the growing impatience and frustration of younger Democrats, who are now moving into leadership posts and feel their party must modernize its message to the electorate.

A group of conservative Republican senators called on President Reagan today to counter what they said were Soviet violations of arms control agreements. On the eve of Secretary of State George P. Shultz's departure for arms talks in Geneva with Foreign Minister Andrei A. Gromyko of the Soviet Union, the senators also urged Mr. Reagan to make full Soviet compliance ''a precondition to serious negotiation.'' The senators made public three letters, all dated today, to Mr. Reagan, urging a tough stand on the verification question. Bipartisan Praise At the same time a bipartisan group of Congressional leaders praised the Administration's plans for the resumption of arms control talks. The Administration, anticipating criticism from conservatives about negotiating with Moscow, has publicly stated it would not negotiate away its plans for research on a long-term plan.

Senate Republicans decided today to write their own set of proposals to reduce the Government budget deficit, an extraordinary move that could put the Senate, rather than the White House, in the lead on fiscal policy. The Senate package would be aimed at reducing the deficit to $100 billion in 1988. President Reagan adopted the same goal last month, but because of economic conditions and the President's decision not to make dramatic cuts in the military buildup, the Administration package now projects a $140 billion deficit that year. Another $1.1 billion was added to the President's proposed budget when Agriculture Secretary John R. Block won delays and modifications in the plan to cut farm price supports. (Page 7.)

A woman armed with a pistol shot her way onto a Pan American World Airways jetliner today, wounding an airline employee. She then held four hostages for more than six hours until she was wounded by a team of police officers that stormed the Boeing 727, officials said. None of the hostages were harmed. The woman, who demanded to be flown to South America, first took seven hostages when she commandeered the plane at Cleveland Hopkins International Airport about 3 P.M. She released three of them three hours later, but held an elderly couple and a woman with her 8-month-old baby at gunpoint until a Special Weapons and Tactics team rushed onto the aircraft about 9:25 P.M., according to Joseph Griffin, an agent of the Federal Bureau of Investigation.

On New Year's Eve, 366 days after Sam Todd vanished without a trace, his aunt was summoned to a police station to confront a disoriented young man who resembled the Yale Divinity School student, who was last seen leaving a party on Mulberry Street. ''Am I Sam?'' the derelict asked wistfully. But Doris Todd knew immediately that he wasn't. Instead, he was another in a series of disappointments for the Todd family and the baffled detectives in the Missing Persons Bureau of the New York City Police Department, who continue their search for the aspiring minister who intended to devote his life to the poor. Nonetheless, the Todds reacted with the gentle charity that is their credo, wishing that someone would claim the young man, and grateful that their 25-year-old son, if he is wandering the lower Manhattan streets, at least has scores of people searching for him.

New York City's chief labor arbiter declared an impasse yesterday in the city's negotiations with its municipal unions, paving the way for binding arbitration. If the arbitration proceeds, it would be the first of its scope here. Some of the unions immediately objected to the finding of the official, Arvid Anderson, director of the Office of Collective Bargaining. Efforts of the unions to prevent arbitration could delay it, even if they are ultimately unsuccessful.

Most of the four million people in this harbor city have eased into vacation routines, slipping away from their high-rise offices early on Fridays in search of the perfect beach. Their coolers brim with beer; their bodies, scorched by the sun, are beginning to assume the gloss of dark mahogany. This time of year here is much like August in New York and Washington. Canberra, the nation's ultramodern capital, designed by an American architect, seems empty.

A top Indian Government scientist was quoted today as saying that negligence by Union Carbide led to the gas leak at a Bhopal pesticide plant on Dec. 2-3 that killed more than 2,000 people and injured 60,000. The scientist. Dr. S. Varadarajan, director general of the Government's Council of Scientific and Industrial Research, said the United States-based corporation had been making lethal methyl isocyanate gas in its plant without adequate safety measures or contingency plans for a leak, the Indian press reported. Lawsuits totaling tens of billions of dollars have already been filed in various American courts against Union Carbide, although jurisdictional questions remain unresolved. It addition, it is expected that thousands of compensation claims will be filed in Indian courts.

Twenty-five supporters of the Red Army Faction halted the Amsterdam- to-Munich express train near here today and spray-painted it with slogans backing a hunger strike being staged by members of the terrorist gang imprisoned in West Germany. One supporter of the West German gang was on the train and halted it by pulling an emergency brake, the police said.

The airlift of Ethiopian Jews to Israel was condemned today by the Ethiopian Government, which called the Israeli project ''a gross interference'' in this country's affairs. Ethiopian officials, reacting a day after the Israeli Government confirmed it had flown 10,000 Ethiopian Jews to Israel in recent years, called for a halt to what they termed ''illegal trafficking'' in Ethiopian citizens. Most of the Ethiopian Jews have emigrated from the Gondar region of northwestern Ethiopia. Some are said to have left through legal channels to join family members already living in Israel. But many more have evidently crossed the border into the Sudan, from which they have been flown to Israel.

Fourteen East Germans abandoned a four-month sit- in at West Germany's Embassy in Prague and returned home today, West German Government officials said. The move left 14 people who are seeking passage to the West holed up inside the embassy in the Czechoslovak capital, Bonn officials said.