Lisa,

You bought a Benz wagon in the first place, which is good evidence that you are not crazy. These are good cars. If you have to fix something, that's just a cost of motoring.

I suggest that, at the minimum, you check your motor mounts, and maybe just go ahead and change them. My daughters car had a slight miss and it got to a terrible point of shaking. Two new motor mounts and you could hardly feel the weak cylinder.

My guess, without seeing the car to tell how bad it is, is that running some "miracle in a can" through the tank as the previous reply suggested, along with a set of motor mounts will make this problem tolerable.

Best of luck,