This happens to me all the time, its to do with a faulty door actuator normally the front or rear passenger door goes faulty, symptoms normally happen when trying to lock the doors then they unlock themselves, will lock when engine is running with key in the ignition (shouldn't do this). Replacing the faulty actuator fixes it. Normally to find the faulty actuator, sit in car, close the locks using the remote, look at the door handles, one will be opposite to the others, i.e drivers door lock open and passenger lock closed, this confuses the central locking mechanism and so it opens the locks not knowing that one of the actuators is actually the opposite to what the controller thinks, this causes the door locks to cycle then stop. I normally get round this by manually closing the offending doors lock closed, exit the car, then lock it, you can tell if the doors are locked becuase the interior light will go off after a few seconds, good luck.
@Rasitlin, think SDD only stops the door locking when travelling over 15mph, not when stationary.