I've seen at least 10 items cause this type of complaint. Did the dealer give you a print out of all codes retrieved from the computers. There are at least 3 computers that should given them some idea of the problem. Many times the problem comes from a "weak" throttle return spring or defective brake switch. The throttle actuator is also a common HIGH $$$$ part that will cause this problem. Ask them to cough up the codes that were found & then a better diagnosis can be surmised!
MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. TECH
190E 2.3 ITS RACECAR