I'll post this to the entire list, so it might help more than just you.

This is a common-ish problem. It's probably due to very cold (and old)
lubricant on the starter. It will prevent the gear from sliding an
engaging.

You could try heating the starter up, or, as I've done before, tap on the
solenoid (the little round appendage) lightly with a hammer or whatever.
Be careful not to short out any terminals, etc. It might take a couple of
tries, but it always has worked for me in the past.

Good luck, and stay warm!

Jon