stalling 300CE

I have a 1993 300CE AMG with 110,000miles. It runs very well most of the time bur occaisonally I have noticed that when I make a u-turn to the left and the engine is idling as I complete the turn, it will stall suddenly. It restarts promptly and may then be OK for weeks. It only happens when the engine is warm. Recently I noticed that occaisonally when revs are around 600 at a stoplight or simply coasting slowly, there may be transitory hesitation and the revs drop to about 450 before rising back to about 600. Has anyone had a similar problem? What is it due to and how do you correct the problem? Thanks for your help. Mike newhouse