What was going on when I was born?

The Sun Belt has begun to rival the North in the level and sophistication of criminal activity, say law-enforcement officials across the South. The growth is marked not only by the influx of drugs, particularly marijuana and cocaine, the officials say, but also by organized car theft, prostitution and pornography rings and complex fraud and money-laundering operations. With it has emerged a new criminal class, which some Southern law officials, for lack of a better term, term the Dixie mafia. The expansion of crime in the Sun Belt was illustrated by the evidence presented in the trial of Charles Voyde Harrelson, who was convicted Tuesday in San Antonio of killing a Federal district judge for $250,000. Mr. Harrelson acknowledged on the witness stand that he got a suitcase and a paper bag of money, about $190,000 in all, from Jamiel (Jimmy) Chagra, a drug dealer. But he denied shooting Judge John H. Wood Jr., saying the money was part of a ''drug scam,'' not a murder plot.

How is it that three conservative Republican Senators can frustrate the will of President Reagan, the leaders of both parties and the overwhelming majority of the entire Congress? The Senators used a filibuster to deal a crippling and perhaps fatal blow to an increase in the Federal gasoline tax sought to finance highway repairs and aid mass transit. By contrast, 48 other Senate Republicans today urged the leadership to do everything it could to revive the measure. Enraged Senate Republican leaders bowed to the filibuster Thursday and withdrew floor consideration of the gasoline tax increase and highway legislation, acknowledging that any delay made passage difficult if not impossible.

The Senate, working around the clock in an attempt to adjourn before Christmas, today adopted a compromise endorsed by President Reagan that would allocate the money to build MX missiles but prevent him from actually spending it until Congress approved. The President sought, and won, a provision that would force Congress to vote on the missile system this spring and not delay the matter indefinitely. On Wednesday the Senate Appropriations Committee passed a similar measure but left out the time limit. Mr. Reagan announced that he would name a bispartisan commission to study how to base the MX before he made new recommendations to Congress. (Page 13.)

Despite two weeks of trying, the Governor and legislative leaders have been unable to reach an agreement on how to close the Metropolitan Transportation Authority's budget deficit and hold off a rise in the transit fares. Early today, the leaders met in Governor Carey's office and decided to take the weekend off to consider the impasse and weigh public opinion. Here are some questions and answers about the situation, based on interviews with participants in the process: Q. What is the problem? The M.T.A. projects deficits in the 1983 calendar year of $187 million in the $2.2 billion budget of the Transit Authority and $117 million in the $900 million budgets of the Long Island Rail Road and the northern commuter rail lines. These deficits have occurred largely because a tax package approved by the Legislature in June 1981 is producing about $300 million less than expected for the M.T.A. When they passed the package, the legislators said it was to hold the subway and bus fares to 75 cents for two years.

As OPEC ministers gather in Vienna to discuss ways to reverse the fall in oil prices, industry experts foresee the possibility of a substantial decline in those prices during the coming year. These predictions of a continuing drop from the basic $34-a-barrel level have sparked fears that major exporting nations such as Mexico and Nigeria might lose so much in sales revenues that they could not repay their large foreign debts. This could place even greater stresses on the already strained international banking system. However, in a spot survey of economists this week, most said a moderate decline - say, $5 or $6 a barrel - would prove so beneficial to world economic recovery that the pluses would far outweigh the minuses.

The Justice Department said today that it would refuse to follow a directive from the House of Representatives to prosecute the head of the Environmental Protection Agency unless it was ordered to do so by a court. House officials said the action showed that the White House was advocating obstruction of justice and setting the stage for a constitutional crisis. The Justice Department filed a suit challenging the House shortly after the contempt citation against the E.P.A. Administrator, Anne M. Gorsuch, was voted Thursday night. Assistant Attorney General J. Paul McGrath, who heads the department's civil division, said today that the House's directive for prosecution would not be followed until that suit, Government of the United States of America v. The House of Representatives of the United States, had been decided.