My 97 grand prix gt will randomly not start about every 3 months. Most recent was 12/21/12 after driving 20 miles home after work. I stopped and turned the car off to grab the mail. When I went back to the car I tried starting it and nothing. No lights, no gauges and no clicking from car. This is exactly what it does about every 3 months. I've had the battery and alternator tested and both have passed with no issues. I just recently found out the power steering pump needs replaced but not sure if that would cause the issue since its been going on for a while. Any thoughts?