03 pt cruiser occasional horn blow

I have an occasional problem with the horn going off for no obvious reason.  The car is equipped with an RSX 3.5 remote start with a shock sensor.  This can happen in my garage or in a mall lot when the car is un-occupied.  The horn will just start going off and I can stop it by pushing the unlock button on the Clifford fob.  The car also has a factory alarm.  Any thoughts? 

not familiar with RSX 3.5, but if its just remote start with shock, what does the shock sensor trigger? does it trigger the factory horn? give some more info on how it works, siren, horn, or whatever.