The handbook does say that the alarm can go off if the cars main battery goes flat. It may be worth checking its healthy and not giving some fluctuating outputs. Maybe also change the battery in the key in case the system is getting interrupted signals when setting.
I dont know of any easy way to disable the alarm long term . Not sure its a good idea. Your Insurers would probably object anyway.
I am assuming its just the standard system and it hasnt been extended in any way by adding movement/shock sensors that respond to a window being smashed, and can activate in high winds or ,heavy rain or if someone bangs against the car. These are notorious for false alarms. And it was not unknown in the past for miscreants to repeatedly provoke your alarm to activate, either as a prank, or until you finally despair and leave it off, whereupon they could break into the car. But this was back in the days where false alarms were so common that starlings included them in their bird song repertoire and people largely ignored an activation.
