Motor mounts commonly fail, causing engine vibrations to be transferred to the body. Failed motor mounts should be replaced in order to prevent damage to the transmission mount.
Car Problem Reports
Mercedes-Benz 300SEL Motor Mounts Fail and Cause Vibration in Body
Mercedes-Benz 300SEL Problem
Visitor, 1991 Mercedes-Benz 300SEL, 157,000 mi
My motor mounts are destroyed and my car vibrates at idle. As soon as I put my foot on the gas though it stops and its as smooth as cream and a lot of power.