Freelander 1 Smoke through vents

I apologize for formatting and being a totally newbie but I was wondering if anyone can help?
I have a Freelander 1 Serengeti 2003 model which for the most part has been a dream!
The past couple of days however there has been some white smoke coming though my air vents in to the cabin. I haven't been able to smell anything. (nothing electrical or coolant)
I haven't been using the air con and I don't think I've turned it on in the 4 years I've had her. It only happens once it's been driving for about 10 minutes or so in the morning, on my way home from work I haven't noticed any. Everything still works, lights, windows, locking .
I was thinking it could be the of ignition wire? But before I start taking it apart has anyone had this happen or any thoughts? I checked all the fuzes in the internal part and they didn't seem blown.
Thank you so much for reading and any help!

If you can't smell anything, are you sure it's smoke? What about condensation or rain water getting into the heater matrix and evaporating as it gets hot?
Do the windows steam up at all?

petrol or diesel FL if the later it maybe the FBH,it maybe coming on when it shouldn't be, it should only come on when outside temp is 5c or below.,

Thank you for replying, it is the petrol version, I'm pretty sure it's smoke just by the way it swirls and it's very white, vapour isn't normally so thick, the windows don't steam either. It did happen for the first time in the rain but the second was a dry day.

I've no idea! Plastic will smell, so that rules out any wiring, connections etc