A clogged cat. converter or restricted exhaust can give these symptoms. When the car is cold, grab the converter and give it a shake. If you hear any rattling, you've found your problem....the ceramic monolith inside is breaking up and restricting exhaust.
Beyond that it could be something like a weak fuel pump, clogged sock filter in the tank, or something else with the fuel delivery system.
Or perhaps the ignition timing or valve timing is off.
95 E320 Cabriolet, 131K