I have a 98 4cyl sonoma and a couple months ago I received a "special bulletin" saying some sonomas might have problems with a piece of the inner lining of the front exhaust pipe might break off and tumble into the catalic converter causing either a rattling noise and/or lose of power and illumination of the MIL. What my truck would do is I'd be driving and all of the sudden all my gauges would bounce, all my lights on my information display would blink and my truck would cut out. It normally would start back up but my MIL would still stay on and the problem would happen again shortly after. Sometimes if I leave it sit for a half a day or so the light would turn off. I had taken my truck to a GMC dealer and they replaced basically my whole exhaust. Only a couple of weeks later, the exact same thing started happening again. So if anyone could drop a few hints, that would help a poor college student out.

I'd be looking toward the ignition switch.