Minecraft causes severe lag on my computer

So I recently started playing minecraft again, with 1.14.3 being the latest version at the time. Lately I have been experiencing severe lag issues after a while of playing. The only way I can track this is of course the FPS

 

So usually I play at approximately 40 - 60 fps in-game. This is consistent for a while, until out of nowhere I get 10 - 18 fps. I suspected this might be due to the graphics card throttling itself due to heat, but this problem does not go away. This lag branches out to the rest of my computer, even with minecraft shut down. I experience sever lag in other applications as well.

To solve this problem, I have to restart my laptop, and then the aforementioned sequence of events restart.

 

What is the reason for this problem, and how do I fix it?