I am curious, what is consitered cold where you are at? I live in the N.E. but we don't seem to be having much cold weather here any more. Generally don't have cold cranking issues until well below freezing. Maybe starting but not cranking. Like the weatherman says "make sure your battery is up to good working order, use lighter motor oil, check tire pressure, and carry a cell phone". At real cold temps, a seemingly "good" battery can cause problems. The easiest place to start is to clean your terminals[batt., solenoid, and starter] and grounds. If the battery is 4 years old, low quality, or if you are not totally sure about it, have it tested and not just witha volt meter. Make sure it produces the sustained voltage and cold cranking amps needed. If nothing changed, go for the starter. Clean and lube where needed, the brushes, terminals, bendix drive and bushings or just replace it. Most likely, with a good battery, it is just loose or dirty connections.
Sorry, I tend to ramble but that's what I would do. I can't think of anything else but I'm sure there is.