Massage, pass key fault

There is a micro chip inside the head of the igntion key, when you put the key in the igntion the sensor inside the steering colunm will read the resistance of the micro-chip. If there is a match the engine will start. If for some reason the sensor will not read the micro chip the system will think some is stealing the car. I would try another key 1st, if this persist, the module will need to be replaced. Start with a new key, its cheaper.
You'll need to go a GM store parts departement with the old key, drivers license & registration for the dealer to cut a new key.