i had something like this, but it turned out to be my sprint-booster failed.

the code that came up was an 'throttle-pedal' failure, so the benz dealership wanted to order me a new pedal. i told them to just disconnect the sprint booster and clean up the pedal and sensor already on there.

lo-and-behold, worked like a charm. if you get a code for the throttle-pedal, just take it apart and clean it up.

make sure you get the ECU scanned. don't waste so much time at the dealer!