98 Accord alarm problems.
 

We have a 98 Accord, and about 3 weeks ago, intermittenly, the factory alarm will start going off. We shut if off, unlock and relock the doors, but will go off again about every 10-15 minutes. We were manually locking the doors and not using the keychain, and that seemed to solve the problem until this morning. Same thing started happening. I manually locked the doors, and by the time I walked back into the house, it was going off again. The only way to stop it this morning was to keep the doors unlocked. Any suggestions????? Nothing has been changed on this vehicle to have caused this to happen. Just started doing it out of the blue on day/morning.