Hi. It sounds like you have very low coolant in the system. Start by checking the coolant level with the engine cool. (There will be pressure and heat otherwise, you could get burnt) Remove the cap and see if the radiator is full. If its not, check for coolant leaks. The most common are the thermostat, timing cover, the back intake to head joints, possibly freeze plugs, or the radiator tanks. It could be a hose or the water pump too, these would normally be larger leaks that you would have noticed.
If you don't find any leaks, replacing the thermostat would probably be the first place to start. Follow the top radiator hose to the engine and you will find the housing. Its easier to remove the a/c compressor to be able to clean the intake better if you don't have access to air tools and a thermostat cleaning tool. Disconnect the battery, the positive post on the alternator is close to the thermostat housing, you could accidently hit it. After you get the new thermostat in bleed the cooling system.
Fill the system and leave the radiator cap off. Start the engine. As it warms the coolant level will come up. It will be up and down a little, and then it will go down a bit and you'll get some bubbling. This is the thermostat opening the first time. Top the coolant off again because it will have gone down. Let it keep running and you should see the same thing happen again. The level will be up and down and be unstable, it may spit some back out (be careful, its hot), and then it will drop. When you get his second drop the thermostat has opened for the second time. Feel the heater or the heater hoses to make sure they are hot. If not, leave the cap off and raise the rpms a few times to circulate coolant faster and get the air out. When the air is out cap the radiator and top off the overflow bottle.