If the engine is not spining fast enough then the engine wont start. This could be the battery and or the starter. Try the cheaper thing first, the battery. Also clean your ground connections. Cold weather kills the batteries in a heart beat.

__________________
1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair