Over Heating

If your Mac overheats to the point it shuts down a hardware problem is likely. Apple Diagnostics will readily identify an inoperative exhaust fan, for example: How to use Apple Diagnostics on your Mac - Apple Support. If the fan is working its efficiency might be reduced by an accumulation of dust on the fan blades or its cooling fins. If dust is a factor it needs to be removed and not just blown around inside.

Other suggestions which ought to be obvious include not surrounding it with insulating material like pillows or blankets, not covering its case with "skins" or the like, and never put anything over the keyboard. Please read Keep your Mac notebook within acceptable operating temperature including all the "tips." They're important.