What happened was most likely that the "limp home mode" was engaged. But as I have experienced it can be many reasons why. In your case, since the car behaved normal so soon again, it might have been a missed spark in the ignition and so to protect the cat, the computer turned it into limp mode.
If it comes back, go to your MB shop to get a diagnostic reading, since most of the information is stored in your car. However if the reason is a bad contact it can be harder to diagnose. Then you might find some clues if you search the forum under "limp mode". (This mode cut your revs at about 1.500)
Good luck!
L.