Air bag light flashing

I just bought a used 97 Tahoe. Had it for a week and now sometimes after the truck has been running for a while, the air bag light flashes. When it is on, I have no throttle control. It flashes in .5 sec intervals. This last for about 10 seconds. After it is done, the transmission shifts extremely hard. It only does this after the air bag light gets done flashing and the hard shifting lasts until I shut off the vehicle. Any ideas? It is 4wd 5.7L

Needs to be scanned on an SIRS function scanner for codes and diagnostics.

Like Max says "needs to be scanned..." I did a "quick" look at my '98 manual and couldn't see any corolation (sp) with the other 2 things, no throttle response and hard tranny shifts. Leads me to think there's something else happening. If the light was on steady that would indicate a definate problem. If the light is flashing that would seem like a loss of power problem, which could also cause the other 2 things to happen. Just thinking out loud and putting them in print. Probably just confuse you some more. Definately get it scanned "for all codes" and post back............Steve