Forget the device, I'd be more concerned about Fire if it really is getting that hot. As said, I would reflash. If it's still acting up I'd take it to a nokia center ASAP.

There was that problem with batteries overheating and exploding, even iPhones have been doing it when getting too hot. It it is hot and isn't just warm, I'd get it looked at ASAP and would advise not using it.

my N900 gets warm, but I'd never describe it as hot. It's passive cooled but no way on earth should it be getting hot hot.