wont start when its cold (98 mystique)

[marcel.crash]

98 merc mystique 2.5 liter 24 valve

driving in a very cold stormy day and it just stalled and will not restart , cranks over fine , when i cicle the key i her the fuel pump run for abought 14 seconds . but when i crank the engine over theres no ground signal to the fuel pump relay and no spark at the ignition coil. but after leaving it sit in the shop with the heat on over night the car started and runs fine , i put it out side ran it for 2 hours it ran ok so i shut the engine off. two hours later it will not start again no spark and no ground signal at the fuel realay, pushed it back in the shop let it sit over night with the heat on and it started again and ran ok put it back out in the cold for a few hours and it wont start .
any ideas ?