This is indicative of one of the locks not quite engaging so it unlocks and tries again. Unfortunately there is no easy way I can think of to isolate just where the problem is but it could be:
one or more doors or boot not quite latching - usually adjustment of the lock strker will fix
one or more sticky locks - some lube (NOT WD 40)
one of the flexible wiring harnesses or connectors in the door pillars or the boot lid
Does the car lock normally on the fob?
Try deliberately leaving each door in turn latched but not shut and see if that changes the behaviour
Disable auto lock and see if that changes anything.
With the car running but not moving can you lock the doors on the switch?.
