I'm not sure if my problem is exactly the same as yours, but on my 1989 300SE, I once had an intermittent loss of power problem. I changed first the over voltage relay, and later the fuel pump relay. Did so after doing the usual tune up stuff--new rotor, cap, wires, plugs, none of which solved the problem.

Anyway, because the problem was intermittent, I changed the relays on the advice of an MB tech friend of mine. Whatever it was, the problem seems to have gone away. Have not had it for probably 5,000 miles at least.

The over-voltage relay, I'm told, can cause many weird things. As has been suggested, it would be best to take it someplace with good test equipment, but if the problem is not in evidence when you do so, I suspect they will not find the problem. Both relays are easy to change, by the way--located between the firewall the the engine encapsulation wall. Best of luck.

Joe Bauers