Steve and Joe,
Well I'm not a nuclear scientist but neither did I fall off the truck yesterday.... I took my car to more than one place trying to determine the source of the problem but got no clear diagnosis. One of those places was the local mercedes dealer (twice). I also checked in with a number of mercedes web sites (such as this one) and found no consensus.
I paid to have most of the work done because I saw no option other than to live with the vibration....which I can't accept. I'm definately shooting in the dark and would greatly appreciate advice from anyone who has something to offer.
Nic in SC