As far as I know your car/year only will set off the alarm if the trunk/hood/doors are opened after the alarm is set. It does not have any motion or shock sensors. Try this, roll your window down and then get out of the car and lock the door with the key. If you reach in and pull up on the lock and then open the door, the car alarm should go off. The alarm is just the horn beeping. To turn off the alrm use the key to unlock the door-lock the door-then unlock the door.
Good luck and let us know what happens.
ARI