This is going to sound a little wierd, but make sure your battery cable connections are
clean & tight.
My air bag light was doing the same thing a few winters back along with other electrical gremlins that would come & go at will. I started checking a few things, and pulled out a multi-meter. I checked the voltage at the battery posts and at the battery cable and found some bad connections. I was out on the road, so I picked up a battery post brush and a bottle of Coke. After cleaning the connections real good and making sure they were tight,
ALL of the problems went away including the air bag light.
