I agree with txsilver. I know what a pain it is to drive in winter, I live in the Northeast, but if there is a compressed nerve somewhere causing this, the longer you put it off, the less are the chances for the nerve to regenerate. Then you could be stuck with the numbness permanently. It could be something totally different, and I'm not a doctor, but just in case it is nerve related, you should act soon. I know about the nerve damage because I have osteoarthritis in my spine with some stenosis (causes compressed nerves).
Keep us posted.
D.
The advice you have received to this point is good advice. If it is really bothering you and is not going away, you need to see a doctor and have it examined.