A few years ago I had a sensor go bad in my deck lid.
When the car was parked and locked it would just go off.
I'd Lock it up and get about 20 feet away and it would start hollering at
me.

I claimed that it didn't want to be left alone. It was funny the first
couple of  times, after that became pretty annoying.
Replacing the sensor in the deck lid was the cure in my case. Your mileage
may vary.

You may want to have the system and sensors checked.

Kate
98 Cobra Drop Top