Are you sure you are getting collision warnings or are they the parking sensors? My parking sensors detect movement when my car is stationary.
It's collision detection because it flashes the image of a car and an exclamation mark in the display whereas proximity sensors don't do that. I have to admit I'm confused now because it's clearly only supposed to be a forward warning and uses the forward facing camera to trigger.
But on the three or four times I can remember it happening there was definitely nothing in front to trigger it. At that roundabout incident I was stationary and so were the vehicles in front. Another incident on the A34 I was minding my own business in lane one at 60mph with quite a gap to the vehicle in front (which I was keeping pace with) and someone came up behind and did a very late overtake. Then a couple of weeks ago I was in lane one of the M40 approaching J10 at 60mph keeping pace with a van that was also indicating to pull off. A vehicle swerved in behind my and the alarm triggered. I remember thinking that it was a typically stupid driver because there was space in front of me that they could have safely dropped into.
My car has done some odd things over the years but this makes no sense. The only incident that
might and it's stretching things a bit is the roundabout one where the camera might have picked up a reflection of the passing vehicle in the car ahead's rear window. But that doesn't explain either of the other two incidents I can remember. On the A34 and M40 there was no vehicle close enough for that.