Overheating MacBook Air in backpack

my MacBook Air just overheated in my backpack to the point it alsmot hurt to try and it out, I’ve had this computer for a few years now and it has never done this to me I haven’t changed what I use it for day to day

It overheated like the fan way working out of control then I left it on a flat surface for about 2 hours and it was back to normal when I put it in my backpack to leave and then got to my destination and took it out it was so hot the whole MacBook Air

[Re-Titled by Moderator]