system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why my computer can be running along fine, and then suddenly slow to a crawl for a few minutes?
gpt
Your computer is doing a lot of things in the background.  You have things running to index files in the background so searches go faster, software updates, virus scanners and countless other things happening without you actively trying to access them.  On top of that, any random activity might just push your memory usage up to the point where you have to start swapping RAM to your hard drive.

Let's say you're at a restaurant and your waitress is prompt and always filling your coffee.  What you don't know is that the dishwasher got sick so at some point she has to go wash the dishes.  If you want more coffee you're stuck wondering why you're not getting service with no explanation.