What was going on when I was born?

Senior Administration officials said today that there had been new Israeli military movements near the Lebanese border over the last 72 hours, causing grave American concern about a possible Israeli assault into southern Lebanon. The State Department, in response to inquiries about an Israeli military buildup, said through a spokesman that it was aware of the reported movements and of ''an increase in tension in the last few days.'' Says Cease-Fire Was Violated ''Once again we renew our appeal to all of those involved or with influence on those involved to show the utmost restraint,'' the spokesman, Alan Romberg, said. ''This is a time for maximum caution. We, for our part, through our continuing contacts with a number of governments, are working energetically to encourage an end to all actions that contribute to tension and violence.''

Blue-collar workers at the General Motors Corporation have narrowly approved a new labor contract that includes wage and benefit concessions to management. The final vote was 114,468 in favor and 105,090 opposed, only a 52 percent majority of victory. A similar contract at the Ford Motor Company was approved by almost 3 to 1 in February. Douglas A. Fraser, president of the United Automobile Workers, said today, ''The closeness of the vote makes it clear this was a very difficult and painful step for our U.A.W-G.M. members, yet one taken in an attempt to address our problems in these very troubled economic times.'' Union's Biggest Concessions The new contract represents the first time General Motors workers have agreed to open an existing labor agreement at the company's request, and the economic concessions granted were the largest ever made to the company. Both General Motors and Ford have laid off thousands of union workers because of seriously depressed automobile sales.

British officials said today that time might be running out for a peaceful settlement of the dispute with Argentina over the Falkland Islands. The officials said that only Secretary of State Alexander M. Haig Jr. had a chance of persuading Argentina to withdraw its troops from the Falklands so that negotiations could begin before the British Navy imposes a blockade in the waters surrounding the islands. Effective 12:01 A.M. Monday, Falklands time, Britain has threatened to sink any Argentine ship found within 200 miles of the islands. Haig Flies to Argentina Mr. Haig left here early today on the long flight to Buenos Aires. On his arrival there, he said the Reagan Administration's improved ties with Argentina were ''a good basis'' on which to resolve the crisis. Earlier, more Argentine troops were reported flown to the Falklands, and a rally to demonstrate Argentina's national unity was scheduled for Saturday. (Page 6.)

The Producer Price Index for March fell onetenth of 1 percent from the previous month, the first time in more than six years that this broad inflation measure has declined for two consecutive months, the Labor Department reported today. The index also declined by one-tenth of 1 percent in February. Energy prices fell in March even more than in January and February while food prices, somewhat surprisingly, reversed course and turned down. The figures were seen by economists as more evidence of the progress made against inflation, though they cautioned that much of the gain reflected the persistent recession that many think has already touched bottom.

In the 1970's, the decade of Houston's most prodigious growth, nearly 700,000 workers joined the labor force here. Most of them did not belong to unions and still do not. Now the A.F.L.-C.I.O., responding to what it sees as its premier opportunity of the 1980's, is trying to add half a million or more new members to union rolls here in what appears to be the labor movement's most ambitious organizing effort in at least 20 years. If the campaign succeeds, labor will have invaded the historically nonunion South as never before, at a time when the union movement nationally has been faltering. The American Federation of Labor and Congress of Industrial Organizations is committing $1 million a year and 20 full-time organizers to the effort, which it says may last 20 years.

A State Department official said today that the United States had offered Nicaragua a new plan that would mend relations in return for an end to that country's support for insurgents in El Salvador. In essence, the eight-point plan provides for the resumption of American economic aid to the Central American nation, a pledge of nonintervention in Nicaraguan affairs and pressure against Nicaraguan exiles in the United States plotting to intervene in Nicaragua. In return, Nicaragua would have to end aid to guerrillas in El Salvador and agree to limits on heavy arms and foreign military advisers in Central America. The arms question has been the stalling point in past attempts to start negotiations.

A Chicago art transporter told the police yesterday that his rented truck containing paintings and sculptures valued at more than $1 million was stolen while it was parked overnight in SoHo. Detective Robert Volpe, the Police Department's art-theft specialist, said that among the works were 21 painted wood sculptures by Louise Nevelson, with a total value of more than $500,000; an oil by Ellsworth Kelly, said to be worth $85,000; an acrylic by Roy Lichtenstein, valued at $65,000, and a sculpture by Joseph Cornell, valued at $30,000. A Dubuffet sculpture that James Goodman, an uptown gallery owner, said was valued ''in the high five figures'' was also stolen. The police said that all the missing art works had been insured.

A Dutch antiwar group attacked a 60-by-20-foot replica of the White House with sledgehammers and spray paint today, but its designer said he would fix the creation he spent 20 years building. The designer, John Zweifel of Orlando, Fla., said: ''Nobody will ever destroy this thing because we'll build it up again. The world can change, but I don't have to change with it.''

Three years ago, a senior diplomat at the United States Embassy here complained to a friend that, while he loved living on this island, his work was fairly dull. ''This is the kind of place where you have to wait on line to get your reports onto the back burner in Washington,'' he said. Since then, things have changed. This island democracy of 14 million now receives more American aid per person than any other country in Asia. The 31 Americans in the United States Agency for International Development mission form a larger group than their counterparts in either India or Pakistan.

For the first time since he arrived in the Caribbean three days ago, President Reagan relaxed at the beach with friends today rather than rushing through meetings. Several senior White House and State Department aides who came here with the President flew back to Washington Thursday night. The few remaining here have no plans to meet with him until he returns home after Easter church services Sunday. The President spoke to Secretary of State Alexander M. Haig Jr. by telephone for five minutes shortly before 6 P.M. and received an update on Mr. Haig's talks with Prime Minister Margaret Thatcher of Britain on the subject of the Falkland Islands situation. Mr. Haig is now in Buenos Aires for talks with Argentine officials.

The decision by the Rev. Billy Graham, perhaps the nation's best known religious figure, to address an international conference on disarmament in Moscow next month adds a powerful force to the growing drive by church leaders to end the nuclear arms race. The momentum of the antinuclear movement among a variety of spiritual figures is building steadily. Religious liberals and conservatives are putting aside their differences. Roman Catholics are standing side by side with Protestants, Jews and those of the Eastern Orthodox faith in opposing further production and deployment of nuclear weapons.

Prime Minister Mohammed Mzali of Tunisia will make an official visit to the United States on April 29, official sources said today. It will be his first visit to Washington since taking office in April 1980.