I have the same problem on my 190E 16V. It could be as simple as a worn motor mount, or a vacuum leak on the throttle area.

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1987 190E 2.3-16V - Euro Spec with Remus exhaust
1996 E320 - Lorinser body kit, Lorinser exhaust, Lorinser 18" LM-5
1992 Acura NSX - Wings West body kit, Comptech I/H/E, TSW 18" Kyalami