I remember reading on a forum somewhere that silicone spray on the rubber weatherstripping on the doors can help prevent them from freezing shut. I was actually thinking of that the other day when my doors got sticky after washing off the road salt.
I actually froze my gas door shut last winter after I washed and drove it out into the -20C (-4F) cold. I had to use a hairdryer thaw it out so I could open it.
My Q has never had a problem starting in the winter cold. I've started in temperatures as low as -30C (-22F) without a problem. Having a block heater really helps though, but I have started it a few times in those temperatures without using it.