98 Camry - Intrusion Detect problem

I have a 98 Camry and whenever you unlock and open the door the alarm goes off.  It doesn't happen every time, but it does happen a lot.  This happens if use the remote entry key fob or the key.  This car doesn't have a full alarm system, just the intrusion detection system.  I'm assuming there is something wrong with that system, but I can seem to find any detailed information on the components of that system.
 
Thanks,
Mike

if all doors /hood/ trunk are closed then the system should disarm itself when you unlock the vehicle. You may need to bring it in to check it out.