Avalon random car alarm activates

After owing this '99 Avalon for 1.5 years, the security system has been activated several times, normally on cold nights. No work has been performed on the car recently. I have changed the remote battery and tested the system per the owners manual with OK results. I'm thinking a sensor needs to be adjusted and may be going out of adjustment due to cold nights, in the teens. The car previously had front end damage. thanks. my Haynes manual has nothing on it but a wiring diagram. pls help as the neighbors are getting annoyed.