car turned off while driving, lights and power steering, everything. Then it restarted on its own, then shut down again. Was able to coast into the entrance of a parking lot, hit the brake (that worked)and physically turn the key and start it again. Before this happened, every time I would accelerate up to about 23mph the locks would automatically re lock. Did this maybe 14 times on this particular drive alone. Heater fan also was making a ticking sound while on full blast. Had it towed to a GM dealership that could not find any problems at all with the vehicle. I have seen this particular problem on the internet with other 2004 Pontiac GP owners that have had no solutions also. I have children ride in this paid off car and am concerned about the situations this problem is going to put us in.