if there's not a loose wire catching on the fan it's probably a bearing, you can try lubricating it but fans are relatively inexpensive compared to other components and pretty straightforward to swap if you'd rather not deal with that

it's probably the bearing yeah—i even cleaned it with compressed air to dislodge whatever's going on. it's a pre built though, and i don't have a way to take it in either (plus i need it for work), so maybe lubricating is the way to go

basically fan spin a lot and over time the bearing gets dry and starts to wear out