Okay so here is the deal - I had this happen and your going to get all kinds of replys but here is really what is wrong (my car sat at dealer for over a month they said nothing was wrong with it).

The locks are air operated - the compressor in the trunk is losing pressure as soon as pressure is gone the alarm goes off - it is that simple - but a ***** to figure out.

-Some will say "is it parked on a hill (so what it should still work)"
-Is the car level
- are the doors closed all the way

IT IS THE PUNUMATIC SYSTEM