Hi W126,
I second rudy's suggestion. When did you have the last tune-up?
May be the fuel pressure is lower after sitting so long. Check-valves for the pumps are only about $ 11 each at Fastlane. It probably is a combination of little things that makes for a poor start when it's that cold. After all, it still starts.
Luckily, I'm in the south ...
Regards
Reinhard Kreutzer