Picked the S2 up yesterday and all seemed well (apart from find out I really need 2 new tyres .. but thats another post)

The car was already running when I picked it up and I drove it up and down the road to check the shortshift was good

Went to start it about 2 hours later and it was knocking on idle, I dabbed the throttle a little and it got louder ... after a few mins it stopped and was well, it drove as usuall.
Went to start this morning (outside temperature was about 3 degrees here) and the same thing happened ... it was knocking. Dabbed the throttle again, and as the revs went down the knocking disappeared. So I started to turn around and the knocking came back, but not as loud. I carried on driving to see if it carried on, and soon enough it stopped and the car was fine.

It's knocked before when cold starting, but not for as long as this time, and it only lasted about 3 seconds (I guess).

I don't think the knocking starts straight away from start (the car starts no problem), its a couple of seconds after.

Any ideas ?