2000 Chrysler Town and Country Cold weather starting

With temperatures under 0 degrees F, I tried to start my van. It initially started, but was jerky and rough sounding. It started but it never idled gently like usual. I turned it off and tried it again after a couple minutes. It kept turning over (almost sounding like it was going to start), but never started up completely. I jumped the battery, thinking it could use some extra "juice, " but that didn't work either. The next morning (today) I pushed it into our Industrial Tech shop at our school to let it warm up and to give myself a warm place to work on it. After knowing the car was warm, I tried it again. It did the same thing. It keeps turning over, but not starting completely. The battery and spark plugs are both pretty new. I do not know if the spark plugs being flooded could be an issue. I haven't had time, but the shop teacher took one out and said he didn't think anything seemed foul. I don't know if there is a relationship between the spark plugs and the starter and I also don't know if the engine would be turning over if the starter were bad. What do you think?