I don't recall if Mercedes has a maintenance requirement on the throttle body.
I do believe, however, that the common fix for a sticking throttle is to lubricate the linkage and to clean out the (for lack of a better word) swivel joints.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".