I have an 04 cts with the 3.6 liter engine. The car runs like a top and has a brand new battery as of just yesterday. The problem is that if it sits for more than 15 minutes it won't start and the key won't come out unless I disconnect the battery and then reconnect it. Battery is fully charged and there is no drain. It only does this sometimes though... Does anybody know why or how to fix it?