I have a similar issue and the problem is that the driver's door latch is not sending the signal to indicate 'I'm open!'. The interior motion sensor is still activated and starts the alarm after about a minute if you move into the car or self-locks again automatically because it believes that no door has opened. If you unlock the car with the remote and open the passenger (or any other door) the alarm will not sound. The local dealership offered to replace the doorlatch switch for me for $740 – I abstained. A special tool is required to dismantle the door lock mechanism.