SHOULD CONGRESS get a pay raise? The question is scheduled to come before the House today. Many members would probably prefer not to discuss it at all. They agree with Rep. George M. O'Brien (R-Ill.), who said last week that even if the job is worth more money, the criticism produced by a raise might be too great. Yet it isn't just Congress whose pay has been the same since February 1977. The lawmakers' own diffidence has kept all other top-level federal salaries frozen, too. Surely senior federal executives, judges and others who are affected are entitled to some added compensation between now and the fall of 1980. If their pay cannot be handled separately, Congress should swallow hard and give everyone a raise.

The next question, then, is how much? Under the automatic annual adjustment system, the top-level increases will be greatest if Congress does nothing before Sept. 30. In fact, unless the lawmakers impose some kind of curb, they and others in the top brackets will get two raises in October, totaling perhaps 11 percent: the 5.5 percent increase that was deferred in October 1979, plus whatever more - perhaps another 5.5 percent - President Carter recommends for the federal work force as a whole.

The House Appropriations Committee concluded that would be too much. It approved a proposal by Rep. John P. Murtha Jr. (D-Pa.) that would limit the total top-level increases to 7 percent. That may still be too high for some nervous lawmakers to explain; perhaps a 5.5 percent limit would be more palatable at home. Neither number has any magic - but either would fall within a reasonable range, between the extremes of an increasingly punitive freeze and an abandonment of restraint.

Two points are more important than the exact percentage, anyway. One is that Congress should address its own pay question straightforwardly, instead of trying to ease some members' financial strains through crafty special tax breaks and the like. The second is that the legislators should avoid creating any more difficulties for those in the other branches of government whose pay is now being held hostage to the politicians' super-sensitivities. Another general freeze could undermine the whole structure of merit awards and incentives for senior executives, which is a central feature of last year's civil service reform. That is one more reason for Congress to find a way to detach its own pay problems from those of the rest of the government.