[Billfitz]

It would pop up because something is draining serious power that shouldn't be. Cold weather makes it worse, but it's not likely to be the only factor. The definitive test is to park the car, check the voltage with a DMM, lock the car. Measure it again in the morning. It should not go down more than 1/2 volt. If it does do the same the next time you park for the night, but this time disconnect the battery negative terminal. The next morning check the voltage again, before reconnecting the negative terminal. If the battery went down more that 1/2 volt overnight it's not holding a charge. If it didn't something that's supposed to be off when the car is off and locked isn't off.