Had a very similar probelm on my w201. The fuel pump relay started overheating after I washed the car and some moisture got inside it. It caused the car to shut down in the middle of the road for a few minutes until the fuel pump relay cooled down, then it would restert and go a bit more until it overheated again. Very annoying.
replaced the fuel pump relay and the problem never came back.
1985 190E 2.3L - a constant project.