[Davescort97]

Welcome to Automotive Forums. Sounds like you have an intermittent drain of the battery. I say once in a while because it it was ocurring all the time it would be a predictable thing. I think you might not have shut a door or the trunk completely and the dome light might have caused the battery to drain. If this isn't the problem you could hook up a light or DVOM between one of the battery terminals and the cable. If the light comes on or the DVOM registers current something is causing a drain. To find out what, make sure the key is off and no dome light or trunk light is on and pull fuses until the light goes out. This will tell you what electrical system is draining your battery.