2002 Buick Century will every so often not start. I get in it and turn the key to start. Nothing. Lights all come on. Lights do not dim. Starter does not make any noise. Battery is new as well as the alternator. If you jump it it will start right up. It might not do it for a year and then it might do it every month or so. No warning lights or bells going off. Been doing this for ten years and the garage has no idea since it will not do it when they look at it.