'92 Rodeo "check transmission" light

I've got a '92 rodeo, automatic transmission, 6 cylinder. About once a week, the check transmission light comes on. When this happens, the car won't shift out of the current gear. When I shut the engine off and restart, everything works fine. I've heard that there's a computer that controls the transmission on this model. Is there a module or something that's going bad? Any advice would be greatly appreciated. Thanks, Dave