I've got a 92 400E and it was doing sort of the same thing. In the moring when on the way to work about 6 blocks out if I had to slow down, the car would start to rumble a bit then all the dash lights would come on and the car would cut off. I would start the car back up and everyhing was fine until the next morning? Took it two 3 mechanics, relplaced rotors, spark plug wires, fuel filter, main wiring harness. Non of that fixed it. Someone on the list suggested using that Techron engine treatment to clean out the fuel system and it seems to have worked so far my car has not cut off on me. This may not fix your problm but its someting you can try and it doesn't cost very much..