Anti-theft Devices problems of the 1996 Chevrolet Cavalier

I am having a very difficult time understanding and obtaining clear information on the 1996 Chevrolet Cavalier's theft system that came with the car from the factory. Something is tripping and I cannot disengage it. When tripped, the engine shuts off and this can happen at any time and at any place, and it has!! I talked to service representatives at three local Chevrolet dealers and all three say very different ideas and none help. Also, the obd diagnosis shows nothing wrong but each visit costs me over $80. 00!! I even called the factory and no one would take the time to answer my questions.