I had a 1990 300E with similar problem. However, I live in southern California and it did not appear to be related to weather. At about 80,000 miles the car would stall intermittently when the car is stopped at a light or slowing down. The car would then start right away and would be fine. The car seem to stall right before the car come to a stop. This would happen probably one out of every 10 stops. Of course, this would never happen when the dealer test drive the car.
After about 2 months in the shop, with almost every sensor and valve replaced, the dealer found the problem with a "speed sensor in the dash board". I am not sure of the exact technical term of the speed sensor. They replaced the relatively inexpensive part and the problem resolved. I hope this is helpful.
BTW, I also had to replace my coolent sensor about the same time. It was corroded and leaking. The coolent light would come on and off at times. While you are at it, check out the neck of the radiator pipe. Again, I am not sure of the technical term. The pipe on the right side of the radiator that the hose is attached to. Apparently, the neck on my car got corroded and it blew my hose off one day.
[This message has been edited by CC (edited 02-07-2000).]