Are you sure the truck isn't moving, causing the motion sensor to trip. I discovered a EAS leak because every night around 3-4 am my alarm would go off. Turned out the suspension would sag suddenly when the air temp got cool enough. Both fgront bags had small leaks.
Try disabling the motion sensor and see if the alarm still goes off. FYI you disable the motion sensor by hiting the lock twice, the red light on the mirror will be solid.
good luck.