Alarm goes off for no reason

[Mabuhay]

Every time that it gets warm outside, the alarm on my X5 goes off. The dealer thought two things:

1) I had a pet inside that set off the motion detector
2) I had the key in my pocket and hit the "panic" button

For #1, we have no pets. Stupid rep kept insisting that I had a pet in there (10 times since they saw that the alarm went off 10 times). Again, we have no pets.

For #2, he then insisted that I hit the "panic" button on the key. That could have been true but since I work from home and my office window faces the X5, they key is sitting on the desk at all times. Again, it's not the panic button.

So what could it be? The alarm did not go off AT ALL during the winter. Now that it's getting warmer, it's starting to go off. I checked to see if the hood latch was bad, but it's not either.

Any ideas?