What to check?

I would check to make sure you have got 12v to the starter solenoid with key on then 12v going to the starter when the key is in the start position if so try tapping the starter lightly, maybe a stuck brush or in need of a starter or solenoid, too bad about the minus 10 here on Vancouver Island we rarely see it below freezing but were in the second week of it now, bring back the rain!