This is probably not it, but just food for thought and/or an amusing anecdote. I guess it depends on how easily amused you are.
So, a long time ago as a wee tot, I had a BMW E38 7 series, which was IIRC the first car that I ever owned with a factory alarm system. It was parked, locked, in my carport. Every-so-often, the alarm would go off. I'd run outside to confront the thief, but no one was ever there. No kids, pets, etc. either. It became fairly frequent.
Then I found a pattern. It only happened when I was making a snack, and often briefly microwaving a small item (like softening a small pat of butter). Further testing showed that it was leakage from the microwave, apparently on the same frequency as the "panic" button on the remote. A new microwave oven fixed the BMW.
So, if it happens to you guys on a pattern, it could be something else (including a neighbor) that is sending out a signal.
I also had this happen to a Porsche 911 I once owned, it thought the radio was being stolen and would set off the alarm. I solved that one by selling the car.
![Boogie :boogie :boogie](/forums/data/assets/smilies/boogie.gif)
Stupid German electronics.