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)