Does your ignition key have a small black piece on it? If so, then you have whats called a VATS system. Basically it's a simple anti-theft deterrent for your car. There could be 2 possible causes: 1) the VATS chip on your key has worn down and is not making contact with the reciever in the ignition cylinder, making the car think that a non-VATs key is trying to start the vehicle and will not start for about 10 minutes, OR 2) the ign cylinder's contact for the VATs key has worn down, causing the same as #1. Rarely, it could be the VATs module, but if it's intermittent, then I would suspect they key and/or ignition switch. Your local GM dealer should be able to diagnose that pretty easily, I used to see alot of those some in all the time. I would recomment though getting it verified that it is VATs related before you start installing parts. I do, though, usually recommend that the ignition cylinder be replaced as well as the key, but again I would make 100% sure that THAT is the problem. Hope this helps!