Pilot, 2005 unlocks by itself

I just purchased a 2005 Pilot EX. Upon getting home and sitting in the garage admiring the interior I heard the door locking mechanism engage on all doors. At first I figured it was some feature like GM has when you shift from drive to park but it continued to happen randomly 4-5 times per minute. I thought maybe the remote(s) were the problem and took them to the other end of the house out of range. That was not it. I then noticed that this happens all the time, driving down the road, stopped at a light, or in the garage with the keys at the other end of the house. The only way to stop it is to lock all doors. If I lock the doors with the remote or master lock it usually stays locked but once in a while it will immediately unlock. If I lock it and wait 5-10 seconds and it doesn't unlock then it seems to stay locked. I have an appointment to have the dealer look at it but it's not until the end of next week.