This definitely sounds like one of those problems that needs to be experienced by someone in person. Prefereably a mechanic or someone familiar with MB.
We can theorize all day and still be wrong.
To me, the symptom descriptions sounds exactly like the tranny problems I had. But that's because that's the only problem i've experienced with the same symptom. I don;t doubt a fuel problem or related system could also create a similar symptom.
Definitely have somone look into it asap. It may cost a lot (or not) to fix, but what is guaranteed is the longer you hold off, the more $$$ it'll cost you in the end.