First up the car is a 2007 Chevy Cobalt LS. Completely stock with a stock remote starter and alarm. The other night the alarm just started going off by itself every so often. I ended up parking it in the garage for the night and did some research. I found that it could possible be the the spoiler leaking and getting into the remote trunk release so I just unplugged it. It seemed to fix the situation for a little.
A few days later the radio is now changing stations by itself, but the alarm wasn’t going off. Now im back to the alarm randomly going off.
When ever I see weird electrical issues I always start with grounds. Take the negative off the battery and make sure it’s good and clean (don’t just look at it with it still on the battery). If that’s good find the main ground for your BCM and make sure it’s good. On the GTO it’s in the engine bay, passengers side front fender since the BCM is behind the glove box.
EDIT: And check your battery as well. Computer modules get wacky with low voltage situations.
Should be between 12.5 and 12.8 when the car is off. Probably worth the 5 minutes to stop by Autozone and have them do a free load test on it too.
Is the stereo OEM too?
I don’t know how GM factory alarms work, but a lot of alarms monitor voltage looking for spikes and drops indicating a door opening (dome light comes on) or someone trying to tamper with the system.
You might have been on the right track with the water leaking in idea. Start paying close attention to when the problem happens. Is it always on a night when it’s raining? Or when the temps warm up enough that any snow/ice on the car starts melting? If water is reaching any electrical connection that has constant power the change in voltage would probably be enough to set the alarm off.