What was going on when I was born?

Western diplomats said tonight that the cease-fire in effect between Syrian and Israeli forces was an ''extremely fragile'' arrangement. In the view of diplomats here, the last two days of fighting may have convinced Israel that the invasion was no longer the surgical operation that it had intended. Israeli losses were mounting, its advance was slowing and criticism was growing abroad and at home, the diplomats said. As late as Thursday, they said, Israeli commanders threatened to move into Beirut and advance to the strategic Beirut-Damascus highway. The Israeli Cabinet's decision to proclaim a cease-fire was apparently made very quickly this morning, according to the diplomats.

Israeli forces and Palestinian guerrillas fought throughout today on the approaches to Beirut and elsewhere in Lebanon as spokesmen for both said the newly proclaimed cease-fires of Israel and Syria did not apply to them. Israeli planes struck a heavy blow at the guerrillas when their bombs scored a direct hit on an apartment building here housing the military command offices of the Palestine Liberation Organization. The building collapsed, reportedly trapping some P.L.O. officials in an underground bunker, but the top leaders were said to have escaped injury. A P.L.O. statement said that more than 100 people had been killed, most of them civilians.

The Reagan Administration has apparently decided to make the best of Israel's military moves in Lebanon by trying to translate them into a long-term political solution for Lebanon. In part, State Department officials said, this course was dictated when Prime Minister Menachem Begin told President Reagan on Thursday that he would agree to a cease-fire but would not pull Israeli forces out until certain conditions were met -namely, the creation of a Lebanese government free of Syrian and Palestine Liberation Organization pressure and the ending of the use of Lebanese territory as a military base for attacks on Israel. Officials said Middle East experts advised Secretary of State Alexander M. Haig Jr. that, because Mr. Begin was adamant, there was no way the United States could obtain an Israeli withdrawal except as part of an overall settlement of the Lebanese crisis. As a result, the Administration decided to welcome Israel's announcement today of a cease-fire and not to make an issue of Israel's refusal to accept the United Nations Security Council demand for an immediate withdrawal.

The Commerce Department announced today that it would levy stiff penalties on steel imports from nine countries, including seven in the European Common Market - an action that seemed certain to bring retaliation against American goods exported to Europe. The Commerce Department's action, if it is upheld on review, would result in the severest and widest application ever of duties against imported steel, a controversial issue for two decades. Common Market officials said that much of the affected steel - representing 4 percent of American steel consumption last year - would be priced out of the market. They said that they would retaliate by imposing similar duties on American exports whose manufacturers are helped with tax benefits and other subsidies from the United States Government.

Israel and Syria announced cease-fires in Lebanon today after a series of fierce tank, artillery and air battles. The truce, which took effect at noon (6 A.M., New York time), did not extend to the Palestinian guerrillas in Lebanon, Defense Minister Ariel Sharon said. The remaining military effort, he said, will concentrate on ''mopping up, cleaning'' a security zone reaching 25 miles into southern Lebanon north of the Israeli border. ''We have to search every cave and every wadi and all subterranean installations the terrorists built,'' Mr. Sharon said at a news conference. Fighting between Israeli and Palestinian forces was reported to be continuing near Beirut tonight, but Syrian-Israeli clashes appeared to have ended, with the cease-fire reported holding into the night.

The New York State Court of Appeals approved yesterday a revised plan by Chief Judge Lawrence H. Cooke for assigning lower-court judges to work as acting justices in State Supreme Court in New York City. The move by the appeals court, New York's highest, ended complicated litigation begun by the Manhattan District Attorney, Robert M. Morgenthau, in opposition to a rotation plan that Judge Cooke put into effect on Jan. 25. The Court of Appeals voided that plan on May 13 on the ground that it had been put into effect in violation of procedures mandated by the State Constitution. The plan approved yesterday is essentially the same as the one that was voided.

President Reagan, bringing his arduous European trip to a dramatic close with a visit to the Berlin wall, challenged the Soviet Union today to move beyond ''the dashed hopes of the 1970's'' to ''a safer and freer Europe'' in the years ahead. ''If I had a chance, I'd like to ask the Soviet leaders one question,'' Mr. Reagan told a thousand cheering American soldiers at Tempelhof Airport here. ''Why is that wall there? Why are they so afraid of freedom on this side of the wall? The truth is they're scared to death of it because they know that freedom is catching, and they don't dare let their people have a taste of it.'' To a separate crowd of 20,000 waving American flags in a windswept park at Charlottenburg Palace, Mr. Reagan drew enthusiastic applause with a pledge that American military forces would remain here ''as long as necessary to preserve the peace and protect the freedom of the people of Berlin.''

The capital of Chad began to return today to its own distinctive normalcy. There were armed men on the streets, although they were from the rebel forces that took the city last Monday rather than the forces that held sway a week ago. The few foreign embassies and international organizations that evacuated their offices in the dusty city last weekend began returning by canoe and raft across the Shari River from Cameroon. There were people running the radio and the ministries and the presidency, although technically Chad has no Government at present and, characteristically for this war-battered nation, those in power by force of arms had no clear mandate from the faction-ridden populace.

The commander of the Organization of African Unity peace force in Chad said today that he had ordered the withdrawal of his troops despite an appeal for them to stay on by the country's new ruler, Hissen Habre. In an interview, Maj. Gen. Geoffrey Ejiga said he had based his orders on instructions from the Organization of African Unity given before Mr. Habre, a former Defense Minister, captured Ndjamena, Chad's capital, on Monday and forced President Goukouni Oueddei to flee. General Ejiga, a Nigerian, had his first meeting earlier today with Mr. Habre. The Organization of African Unity, General Ejiga said, had instructed him to begin withdrawing by today if Mr. Goukouni refused to accept the African body's proposals for a political settlement of Chad's long-running civil strife. Although Mr. Habre has since taken over, General Ejiga said he had not received orders from the organization rescinding the earlier instructions and hence he was going ahead with the withdrawal.

A senior official of the suspended Solidarity union movement has been sent to a mental hospital after a court acquitted him on charges of organizing an illegal strike, a Justice Ministry spokesman said today.

A spokesman for the opposition Free National Movement said today that his party would examine ''irregularities'' in several more assembly races, but otherwise considered this week's general election results ''a moral victory.'' The ruling Progressive Liberal Party of Prime Minister Lynden O. Pindling, which has ruled the Bahamas for 15 years, won a five-year mandate Thursday when a record 76,098 voters elected 32 P.L.P. members and 11 F.N.M. members to the House of Assembly.

Mauritians braved rain today to vote on whether to continue the 22-year rule of Prime Minister Seewoosagur Ramgoolam or replace his pro-West minority Labor Party Government with a left-leaning coalition. When balloting on the Indian Ocean archipelago was suspended for an hour, about 60 percent of the 500,000 eligible voters had cast ballots.