What was going on when I was born?

A major courtroom trial that could throw light on obscure links of international terrorism begins here Monday when five Turks and three Bulgarians face charges they took part in a plot to assassinate Pope John Paul II. The trial has special significance because two Bulgarian diplomats and an official of the Bulgarian state airline are among the accused. According to the state's key witness, they were part of a conspiracy that led to the attempt on the Pope's life in St. Peter's Square on May 13, 1981, and Italian justice officials say circumstantial evidence supports the charge. The witness, Mehmet Ali Agca, who is now 27 years old, is serving a life sentence in a Rome prison after his conviction in July 1981 of having shot and seriously wounded the Pope during his weekly general audience. During his trial, Mr. Agca, who was seized in St. Peter's Square, the site of the shooting, claimed to have acted alone. He later changed his testimony, saying that the assassination attempt was a result of an international plot, masterminded by the Bulgarian diplomats, in which he received the equivalent of $1.2 million from a Turkish underworld figure living in Bulgaria.

Tommy Swan says he has been hearing it since he was a small boy: how the Tennessee-Tombigbee Waterway was going to turn the local economy around and bring jobs and people to this poor quarter of eastern Mississippi. Now, after decades of Congressional scrutiny and sharp public controversy, the $2 billion waterway, completed last December, is to be formally dedicated in ceremonies next week across eastern Mississippi and western Alabama. It links the Tennessee River, in northeast Mississippi, to the Gulf of Mexico, at Mobile, Ala., through a 234-mile long system of locks and canals along the Tombigbee River. ''We waited a long time for it to be built, and I suppose we're going to have to wait some more for the full impact to take hold,'' said Mr. Swan, 57 years old, who owns Tommy's Men's Wear on Main Street. Other stores, left behind by time and the local economy are empty now. ''But the jobs will come -they will come in time.''

The death toll from a cyclone that sent huge waves crashing into the islands of southeastern Bangladesh rose to at least 1,400 today, and officials and survivors said they feared that many more may have perished. One official said the final toll could be in the tens of thousands, including large groups of migrant workers who had flocked to exposed islands to take part in the rice harvest. Several islands in the Bay of Bengal were reported to have been washed away in the cyclone Saturday, which created waves 10 to 15 feet high. 'Beyond Description' ''The devastation in the area is beyond description,'' said Lieut. Gen. H. M. Ershad, the country's President. General Ershad spoke after returning to Dhaka from the island of Sandwip, where he distributed food, clothing and medicine to survivors. He set out in a helicopter but had to complete the journey to Sandwip by sea because of strong winds.

Shiite Moslem fighters in West Beirut have begun killing large numbers of Palestinians from two refugee settlements, according to accounts by witnesses and other reports from the scene. The accounts that are emerging from Beirut come from Palestinians who have escaped the fighting and sought refuge elsewhere in Beirut, witnesses at the scene, medical personnel in several hospitals, Western diplomats and Moslem residents in several sectors of West Beirut. The reports could not be independently confirmed because journalists and the Red Cross were not able to enter the contested area. At Least 250 Reported Dead At least 250 Palestinians, both guerrillas and civilians, have been reported killed in the refugee settlements, Sabra and Shatila. But the total is feared to be much higher.

Four years have passed since a team of business executives went into New York City's bus and subway systems to conduct the most comprehensive study to date of how the Transit Authority functioned and how it could be improved. Finding a sluggish and poorly coordinated agency, with records kept in ledger books, storerooms full of defective parts and monthlong delays in answering letters, the executives recommended nearly 400 specific changes. Officially, the authority accepted most of the recommendations. But interviews with Transit Authority officials and workers and an examination of records found that most of the deficiencies the executives saw in 1981 were never corrected. Management Problems Behind the problems that confront the rider every day - late trains, dirty stations and graffiti-covered buses -lie problems of management that make the Transit Authority an agency that is unsure what it has in its storerooms and that still keeps many records on index cards.

There is no evidence that Gen. Alfredo Stroessner, the 72-year-old President, is ill or is planning to step down, but what comes after his 31-year-old rule is suddenly the main topic of debate in Paraguay. The Government has tried to limit discussion of the issue, arguing that the entire concept of ''post-Stroessnerism'' has been invented by opposition groups bent on agitation. ''There is no such thing as post-Stroessner,'' one official said. But in a country where, in the words of a journalist, ''the news is always the same,'' change is now being viewed as inevitable. ''We're definitely in a pre-transition period,'' a foreign diplomat said. ''Stroessner will stay in office as long as he wants to, but there is genuine widespread concern about what will happen afterward.''

Willy Brandt, the former West German Chancellor, arrived in Moscow today for talks with Mikhail S. Gorbachev, the Soviet leader, that are expected to focus on disarmament and other East-West issues.

Two weeks after a triumphant celebration of the Soviet victory in World War II, a newspaper here has published an account of a Red Army deserter who was discovered recently after spending 41 years hiding in a pigsty. The deserter, bearded, ragged and unwashed, now 74 years old, was found by astonished villagers only after the death of his wife, whom he had terrorized into hiding and feeding him, the weekly newspaper Nedelya reported this weekend. The newspaper said that when the terrified deserter, Pavel Navrotsky, came face to face with strangers for the first time in four decades, all he could find to say was, ''Will I be punished?'' Periodically since the end of the war, the Soviet press has told similar stories of deserters who have been found or turned themselves in after years of hiding. As in the case of Mr. Navrotsky, they are said to have been spared punishment, with the sentiment, as Nedelya put it, that ''nobody in the world could punish him as harshly as his own fear has punished him.''

Gunmen believed to be Basque terrorists killed a national policeman today in the town of Guecho, near this Basque city, the police said. Witnesses told the police that two men had approached the officer, Moises Cosme Herrero, fired two shots at his head and then escaped in their car.

Ten people were trampled to death and 30 were injured today when fans tried to force their way into a Mexican soccer championship match, a Red Cross spokesman said. Crowds panicked when hundreds of fans converged on two entrance tunnels to the stadium before the start of a first division playoff between bitter rival teams, America and the Autonomous University of Mexico.

The Soviet Union accused the United States today of ''overt sabotage'' in the arms negotiations that are to resume this week in Geneva, and warned that no cuts in Soviet arms could be expected until Washington agrees to halt development of space weapons. An editorial from the Communist Party newspaper Pravda dismissed American proposals during the first round of the Geneva talks as ''nonconstructive,'' ''threadbare'' and ''absurd.'' The second round of talks is to open Thursday. ''In practice the United States has no intention at all to reduce its nuclear arsenals,'' Pravda said. It said the United States' affirmations of its desire for arms reductions were ''total eyewash.'' [In Washington, a State Department spokesman had no comment in response to the Pravda editorial.] Treaty Violations Denied Pravda denied accusations by Washington that Moscow is violating the 1972 antiballistic missile treaty, and said American space-weapons research was itself a violation of the treaty. ''The actions of the United States Administration are unlawful by their very essence,'' the editorial said.

Prime Minister Rajiv Gandhi's enthusiastic overture to the Soviet Union last week has produced a shudder of disappointment among American diplomats here. These diplomats have been engaged in the most aggressive attempt in years to improve relations between the United States and India. But they and others said they were convinced Mr. Gandhi would still use his visit to the United States in June to strengthen Indian-American friendship. They argued that his comments in Moscow were in most respects a predictable reiteration of longstanding policies.