I've searched for posts regarding the same problem on a 300E 3.2 and someone mentioned the mass air sensor as the culprit. That kind of surprised me but I pass it on as a point of information. You might consider checking the sensor and connections.
My first thought was the "electronic accelerator pedal" and its wiring harness since that's what controls idle speed. I think the '95 C class cars still suffered from wiring harness problems so it might be worth jiggling that harness to see if the symptoms change any.
Since the 104 engine was used in 124 cars from '93 on you could search for idle problems on 300Es in hopes of yielding more search results.
The problem I was chasing went away during the course of a lot of other unrelated work but the only part I replaced that might have affected the idle was the camshaft position sender.
Good luck and let us know what you find.
'93 190 2.6 Sportline