mine did that a little while ago... i had a leak in my Anti freeeze.. so if i took my radiator cap off... a shit load of smoke came out (cuz it was low on anti freeze.. really low) and then i filled it up.. and the car would go right back to normal.. Now i got a new radiator and never has done it for like 1 month.. but you might have a diff problem.

 

My car had the same issue. Try changing the thermostat. It solved my problem. Its a cheap part and an easy fix...can't hurt to try.