Check your coolant level. If it'* low you need to determine why it'* dropping. You could have a leak in the system (is it wet under the car?). Or, you could have the common intake problem.
If you don't see any signs of coolant under the car and/or under the hood (leaking out) then check your dipstick for a milky substance in the oil. If it is milky, then drain the oil ASAP and further inspect for coolant in the oil. At that point you most likely have suffered an upper intake/lower intake gasket loss.
If there'* no milky substance in the oil, then pop off your thermostat housing and remove the thermostat. You can test the thermostat by heating it up in some water on the stove. If it opens just before the water boils (195 degrees) then your thermostat is cool. Contrary = bad thermostat.
When inspecting under the hood, carefully check the coolant by-pass elbow that goes between the belt tensioner and lower intake manifold. They're known for cracking.