My gas pedal shakes on my C280

I've been trying to figure out why my gas pedal shakes on my C280. I've gone through 2 sets of motor mounts in 9 months, as that was thought to be the culprit. Also my steering wheel shakes along with the gas pedal. I've been through hi speed alignments at the dealership, front suspension basically rebuilt, but got this shaking problem. It's intermitent and isn't associated with a particular speed. Control arm bushings, the whole shabang is new underneath. Any thoughts gents? Also I have a new set of Michelins - no change.

Geoff