Over heating? The only time I find the phone getting hot is using some thing that is data intensive or cpu intensive.
Shouldn't be to different from a regular desktop/laptop computers. Simply because you can go into the BIOS and tell it to restart your pc if your computer gets to hot. I'm sure there's got to be a fail safe with in the android phones.
I don't worry to much about it, in fact I expect it. Did you recently get a new battery? If so it could be a faulty battery. (Just guessing.) As for what I do, absolutely nothing.