Do you have a block heater on your car? If you see an electrical plug near the front of the car by the radiator, thats your block heater. Plug that in and let it sit for a few hours. Getting some heat in the engine makes a world of difference.

Generally, for cold weather starting there are a few common issues:
1. Bad glow plugs
2. Valves not adjusted correctly
3. Weak battery/starter
4. Oil is too heavy (use a 5w-40 in the winter for quicker starts)

All these issues are addressed in other posts on the forum. Just use the search function to find lots of info. Good luck, I've been there.

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1985 300TD 183,000 but I'd rather ride my bike