Sounds like you might have tried to reset the trip meter while moving, a no no. Not sure how to unstick it, try pushing the reset several times in rapid succession, while sitting still of course.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.