My computer does that all the time (not as extreme though). It's fine when playing online, but playing Blockland and such gets it so hot that it overheats and shuts down. I keep a cooling pad underneath (not good enough by itself) and a very small Thermaltake fan blowing into the vents on the side.
Also, I'm sure you've considered it already (due to being obvious) but using your laptop on soft surfaces heats it up really fast (furniture, beds, carpet, etc).