As a GM service consultant for the past 15 years, the most common issue with random alarms is a door sensor is dirty or defective and the alarm "thinks" an intrusion has taken place. You can disconnect and tape the wires on each door sensor, trunk sensor, hood sensor and etc, one at a time to eliminate the culprit. Once you get to a sensor and the issue stops, there you go! I'd say 8 out of 10 have this as the issue.