My 1994 buick regal periodically shuts down while I am driving but immediately starts up again. I have replaced the alternator and fuel filter but it still does it (sometimes when it gets hotter outside). Temperature does not seem to be the specific cause. The mechanic is lost on this. He even drove it for a week and experienced the problem but still cannot figure out how to fix it. Its weird since it just s down and then starts again no problem. It happens when I am driving or stopped at a light so I do not know what is the cause. I have replaced the battery, alternator, fuel filter and water pump.

Replacing the Ignition Control Module (ICM) should solve the problem--easy fix. If I were you, I'd get a new mechanic, too.