overheating? 1991 honda prelude?

today i started my car and the temp gage went right to hot.i only got cold air while idling.once i started to move the gage went back to normal and the heat came on.anyone know what happened? it has never overheated before.also lately when i start it,smoke {blue/gray} comes out of the exhaust.only on first cold start of the day.
 
Top