This sounds EXACTLY like the problem I had on my C280. (see a thread on "C280 limp home mode". No check engine light, ever. Finally, a code showed up on the computer indicating a misfire. Turns out that MB had put the wrong spark plugs in the engine when it was built (it was a crate engine from MB). They put a hotter plug than spec. This with only 1000 miles on the engine. The insulators cracked, causing the engine to occasionally misfire, then causing the computer to shut down fuel to that cylinder.

Symtoms were EXACTLY like you describe. I could also duplicate it on demand. So, I'd look for a misfire problem- plugs, wires, coil, etc...

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Bill Streep
San Antonio
'57 190SL (toy)
'08 S5500 (mine)
'09 CLK550 (wife's)
'06 SLK350 (daughter's)
'11 GLK350 (daughter's)
'03 CLK310 (spare)