Combination of the two previous posts. It's either coolant level or the engine bay cooling fan is not coming on.
Check the coolant level first (when stone cold). If it's low, pull up the trunk carpet and see if there is coolant underneath. If there is coolant under the carpet, then either your coolant reservoir is cracked or one of the hoses coming out of the side of the reservoir is cracked or loose.
If there's not any coolant under the carpet, then jack up the back end on stands and check under the front of the engine for coolant. If you find it here, then you have a leaking hose or the water pump is going out and starting to leak to warn you.
If there's no coolant in the rear, then jack up the front on stands and check for coolant. If you find it, then there's a leaking hose up front or a leaking radiator.
If the coolant is not low, then check the engine bay fan. It should come on at 195 degrees. To get it past the 195 mark, take the car out and warm it up to where the needle is between the 8 and 0 in then 180 mark, then turn around and go home keeping it above 4K rpm. When you get home, listen for the engine fan to be on. If it's not, then you need to test the fan. You can unplug the fan and run wires from the + & - terminals on the battery (preferably not the one in the car) to the two terminals inside the fan connector. If you don't have a second battery, then unplug your battery completely and remove it from the car before doing the test. When the wires are connected, the fan will run if it works. If it doesn't spin, then the fan is probably dead.
If the fan is fine, plug it back in and try replacing the fan relay first to see if it will come on when it should after running the car like before. If it still doesn't come on, then it's probably the engine compartment thermostat. Mine went out and caused this problem awhile ago. It's located in a gromet in the right (passenger) side of the spider. Replace it and hopefully that's the end of it after all of this stuff.
Good luck!
