I've been running into an issue recently where my system will start to stutter and freeze. Going into my task manager (Resources), I can see my using is using roughly 18/32GB of RAM despite closing all apps. Normally I should be at around 2GB on a fresh boot.
I've only noticed this issue appearing when first interacting with an app called Newsflash, but the issue persists even after closing the app. I even tried using systemd's soft-reboot feature and even that did not clear the memory leak. So it seems the memory leak must be in the kernel itself.
And please don't link linuxatemyram. This is not related to cached data.
If you had something hog memory and a lot of other stuff got paged out of ram as a result, that can slow things down. Try running "top" and see how much swap space is in use. If it's more than a little bit, once you have enough memory available by shutting off whatever was hogging it, try "swapoff" (pages the stuff back in, which can take a little while) followed by "swapon" to re-enable swap.