Hello can do........ My car is a 1988 300E 103. Problem was first noticed when it would develop a rough idle at lights or when stationary, not often but enough to be a problem not knowing when it would occurr again. It would gradually get worse and the car could hardly pull it self along, if you could get the reves up it would eventually begin to run properly and everything would be ok.
On checking everything it was found that a suppressor was breaking down now and again causing the problem, I have spoken to other 300e owners and they have experinced similar problems and suppressors have been the culprit. It is hard to believe when it happens that one supressor could cause the motor to run so badly but it does, to the extent that it on one or two occasions stalled totally. I never had problems at high revs.
The overheating was not a symptom with mine.