2008 chevy truck... service air bag light came on a few times in a few days for a few minuets at a time... now it stays on... never hit nothing or did anything to cause it to come on.. any ideals... thanks for your help... richard

Could be corroded sensor under front bumper, shorted wire or other issue.

Could also be a faulty printed circuit board that has some weak solder joints. I've had that happen on mine long ago. It was storing a code for the pre-tensioner but that component tested good. I replaced the sensing and diagnostic module and the light never came back.
It may be best to scan for trouble codes and follow the appropriate diagnostic flow chart and see where it leads.