I have a 92 400E. Had exactly same problem until it stopped recovering and running normally for the duration. Spent over 1000.00 and at the shop nearly a month ( a certified Mercedes Benz shop by the way) and the only thing that they accomplished was to destroy the intake hoses and scratch the door jam when they took out the rear seat. Friend recommended a great shop. 10 minutes...better computer diagnostic capabilities and the answer. Bad spark plug wires. Fixed the problem. Be aware that the wire set from Phil at Fastlane has a one coil wire that doesn't fit the car. It is too short. Good luck.