I was reading this post and realized I never posted my fix. The problem with the shaking was the fact that I would not allow any wheel weights on the outside of my rims. The prior rims were ruined because of it. Mercedes put clip on weights on that they say will not damage the wheels, the car no longer shakes. There is a little cowl shake with the top down, but other than that it is perfect! They also checked the chasis, the engine, suspension, and transmission, they say everything is in great shape. I think it will last for a few more years!