I have a 2000 mazda b3000 and this is the first winter where every time it is around 20 degrees or below outside my truck has trouble starting. If I let it sit in the sun or jump it it will start up so I doubt it is the starter. The battery probably is 6 or 7 years old so that could easily be the problem, but when I checked the battery and alternator with this battery/alternator meter I have both appear to be okay. It seems like something is freezing up and needs time to get warm. This morning it is around 30-35 degrees out and the truck started right up, but after I shut it off I lifted my hood and my radiator fluid was over flowing. Obviously, something is frozen in the radiator, but I never put water in it. I always have put in the premixed antifreeze. Not sure if this has anything to do with the starting problem. Does anyone have an idea what is going on with my truck.

 

How many miles on it? Did you ever flush the cooling system?

Did the engine warm up before you turn it off? If it did not warm up I can see two possibilities for the coolant spill:
A clogged cooling system, or a leaking head gasket.

Get the battery load tested at a parts store. Or replace it right away.