2003 bonneville - door lock/unlock without touch

Hi, All:
I have 2003 Bonneville. This problem happened once a few weeks ago. Yesterday, it happened again. I came home, open the trunk, when I closed the trunk, I heard the door lock and unlock several times, it just looks like someone pressed the keyforb. When I opened the hoop, the light was on and off several times again. The interior light was on more than one hour. Today, I found the battery is completely dead. After the battery is fully charged, I drove to the local road, when I was driving, driver's side door was unlocked from locking position. Later, one of passenger’s side door was unlock too.

Anyone can give some thought for this problem?
Thank you
awu10

Replace the fob. The switch is going to hell. Search on eBay with the code molded into the back.