Problem with fan

I have a side wounted fan on my PC. nothing fancy at all, just a little fan. it spins all the time.
The problem is, when i accidentally bump the pc (not even hard) or sometimes on its own, it starts to go very fast and make a harsh grinding noise that shakes the side of my pc, and causes the whole thing to rattle. it quite loud, and has woken me up severaly times during my beauty sleep. all i have to do is lightly tap the side of my pc and it stops. its only been going on for about 2 weeks. whats the problem? Thanks for any help.

 

Ball-bearing or brush? If it isn't a loose screw holding the fan in, it could be a bad bruh or bearing. Probably the easiest thing to do is pay $5 for a new fan.

 

I was going to say a wire could be brushing up against the blades of the fan, but I don't think that would make the whole case rattle. It is quite loud though. Spend a few bucks and try out a new fan to solve the problem. If that doesn't fix the problem at least you've got a new modding project.