my car alarm goes off after about 30 seconds of locking the door

Theres a little button under the dash where your left knee would be at that the connects to alarm. To reset alarm put keys in ignition to the on position & press the little button & car will honk, & it resets. then see if car alarm is still acting up. Mine kept wigging out so I turned the alarm system off. To disarm the alarm put keys in to on position & press that button down for 10seconds. Your car should still lock, but no alarm sets. To turn it back on, do the same thing but just press the button once & it will honk so now its armed again. Good luck hope helps