Could be battery.
The cold weather makes them work harder and after a drive the battery may have had enough charge to start the car normally the next day.

Age on a battery means nothing.
If you do a lot of small drives the battery never gets a proper charge, best way to test is to do a load test using a proper tool, you CAN use a multi meter and see how big the voltage drop is but it is not as accurate.
You can test the specific gravity of the lead acid using a battery acid test tool(cheap and easy to use)

All batteries need a good charge now and then, you just need to have a battery charging device.