system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what is happening in my brain when a random, insignificant memory pops into my head that i haven't thought of in years?

a lot of the time it happens when i am drifting off to sleep, which is probably a factor, but that isn't always the case. middle of the day, boom, i suddenly remember the time i ran into my friend's parents at sam's club six years ago. we said hello and went on our way. so why did my brain decide i should think back on it with seemingly no trigger?
gpt
Well, the short answer is that no one knows for sure. 



The longer answer has to do with your use of they word "seemingly". There probably was a trigger, just not one you were consciously aware of. It could have been the texture of a wall, a similar physical layout to a room, a scent, a drug in your system, your mood, or even your body position. Your brain codes all of these things into memory, even if you don't know about them. One of these things probably triggered the memory.