BMW Repair Questions? Ask a Mechanic for Answers ASAP
I can imagine how annoying this must be. I have looked over the wiring diagram for your alarm system. The alarm is fed by fuse 26. I think the fuse panel (called the junction box) might be difficult to access but I have the location for you.
A common failure is actually the hood switch. It might be worth a shot to disconnect the hood switch by unplugging the connector. It might be worth trying this before removing the fuse for the alarm.
Make sure the vehicle is disarmed when removing the fuse. If you do choose to try to pull the fuse be ready to put it back in as in some instances the vehicle thinks the alarm system is being tampered with and the siren might sound. If it does place the fuse back in and lock and unlock the vehicle to disable again. If this is the case then the fuse won't be an option unless you want to wait for the internal battery to drain inside the siren (I think it takes an hour.)
The good thing when you get to the dealer it will store what set off the alarm. Make sure to tell them that you disconnected the hood switch in case this was not the main cause as it will set a fault and could confuse the tech.
I hope this information is helpful. Please accept and thank you.