Q: Car misfires and fumbles during acceleration but regains pace. - 2003 Mercedes Benz C230

Hi! The symptoms you describe sound like a misfire caused by ignition components. Running ok until a heavy load is put on the engine, then stumbling and misfiring is typical of an ignition-related misfire. Spark plugs, wires, or coils are the usual suspects, and would be accompanied by a Check Engine Light and misfire codes. A fuel pressure test would provide helpful diagnostic information to confirm adequate fuel supply. An experienced technician, like one from YourMechanic, using a scan tool would be able to look at data that provides clues on which way to proceed. From there, they will be able to diagnose the misfire condition and conduct proper repairs.