Haven't had that issue on my RSQ3, however did have a very similar problem on my previous Mitsubishi Evo. What I found in teh end was that if I reversed it into my drive rather than drive in, it stopped doing it which was rather weird. In discussions with the garage, they suggested that if the front air vents were in a certain position, the possible "force" of air into the car from other vehicles passing the end of the drive (combined with my drive being on a bit of an angle) could possibly be the cause. After the usual "what a load of cobblers" thoughts, I did try it, adjusted the air vents down away (and away from pointing anywhere near the internal alarm sensors) and stroll on if it didn't stop it (it stopped also when I parked the car the other way around as the wind from passing vehicles hit the rear of the car not the front).
So as stupid as that sounds - it did to me at the time - it actually worked. Maybe that may be your cause.
More likely I'd say you have an over sensitive sensor somewhere, maybe try cleaning the push sensors on the doors and under the bonnet and in the tailgate. You could also try disabling the internal sensors when you lock the car to see if that is the issue. Instead of pushing the lock button on the remote once to lock it, press it twice in quick succession. You'll know if it has worked as whilst you hear the car lock and see the indicators flash, the red alarm light in the drivers door won't flash. The car will be locked and alarmed then, but with the internal movement sensors disabled.
