I would suspect either a vacum leak, Mass Air Meter, or Throttle Actuator.
If I was a gambling man (and I'm not), I'd put my money on the throttle actuator.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".