Sounds like a leaking head gasket. Have you been keeping an eye on your coolant level? Or engine temp gauge? If the steam/smoke smells like a dogwood/fish/dirty lady parts then its definitely antifreeze.
The leak completely slows or stops when the engine is warm due to thermal expansion. Your head, block and head gasket expand ever so slightly and fill the void as the engine reaches operating temp. Also the water molecules in your coolant expand as the engine heats up and are less likely to leak through to your cylinder from the water jacket. This is why you have an over flow reservoir in your coolant system.
My '92 legacy blew the passenger side head gasket and it still drove around for over a week. Granted I did leave a long trail of smoke. I suggest NOT attempting to replace your gaskets on your own unless you have the ability to pull your engine and have a second car to drive for a while.