QUESTION IS-
is it really hot, has it got water, ecu fault code, are rad fans on and are there any water leaks?
it may be a faulty gauge, or sender, if it seems to be really hot, and i mean rad fans on and engine bay fans on check the water level and put your hands on the rad pipes at the front, are these also hot?
if you don't feel confident with this go to a garage and seek help as it could get expensive.
if you have access to a scanner do a live data scan, this will tell the true temp via the ecu not the gauge sender.
these do suffer from thermostat probs, something to do with the stat popping out of the holder, but i believe this causes cold running not hot, i may be wrong on this.
any one else on this?