I set mine off inadvertantly about twice a month. The car is in an attached garage, the key in my pocket. If I'm wearing jeans and squat down or lean across a counter; there it goes. Its got a great range. Of course what's happening is the "panic" button's getting squeezed. It is kind of surprising, as setting off the siren is the last thing on your mind.

If yours is going off "in the middle of the night" then that's not it. (I assume you are not up). Are you sure the garage is secure? Do you have any pets with garage access? Good luck. Slo