Several good answers
I got several good answers today. I need to try them. Here are the possibilities: The temperature sensor, cracked vacuum hose, OVP (over voltage protection) fuse or the OVP itself, air flow sensor, O2 sensor, wrong kind of spark plugs, and the possibilities seem to be unlimited!
I thought that Mercedeses ran forever without problems! Maybe, if it was an American car, it would have been already in the junk yard!