PT Cruiser haunted?

I have a very odd problem. When the car has been parked for more then a few hours,
when  I open the door to use it, there is 4 short chimes (one after another) It almost
sounds like a melody with each chime a bit louder then the last. This will continue over
and over until I start the car. It doesn't matter if I'm sitting in the car with all doors
closed, the chimes continue till it's started. Now the odd thing is after starting the car if
I turn the car off, remove the key and exit the car then come back say 5-10 mins later,
it doesn't do it. It's only after the car has been sitting for a few hours. There is no
warning lights on the dash and the car works fine. It's this odd chiming that's driving me
nuts as I don't know what it means. I can't find any information about this on the net so
I'm hoping someone here might know what this mean.