I had a similar problem in my 1988 735i. Turned out that the sway bar end link was bad - causing a metal"clink" whenever I wnet over speed bumps or medium bumps in the road. The link looked fine - but when i banged on the sway bar from below with I fist, I heard the sound that had been driving me nuts for months. It was a cheap fix - $30 for the BMW. Probably the same for the Mercedes.

Regards,
Trpy
1995 E420