Could you post back when they figure out what the problem is? I have the exact same problem with my 190e. Brakes applied very softly at 50-60 will not cause the problem, but if I press firmly, the steering wheel and pedal shake.
I too have newer rotors and pads.
Someone suggested tie rod ends, but I don't know anything about that. I have new wheel bearings too and that isn't the problem either.
Thanks for the help!