You are correct, if the light comes on while driving, it could be indicative of a low voltage - less than 10.1vDC- situation. Could also be a problem with the SRS system too, but likely a voltage problem.
'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.