If you park on a a little hilly driveway, then, that could be the problem. I noticed that most of the automatic transmission car owners when they park, they engage the P first, then release the break pedal. The right way to park your car is to first; press the break pedal, pull the manual (hand) break, then put the gear on N, then release the break pedal (this puts the car weight on the breaks not on the transmission), and finally put the gear on P. Try it and remember this. Never ever put the gear on P before pulling the hand break and leaving the weight on the breaks.