Is it a 3dr? Common enough with them as you're constantly raising and lowering the seat to let people in...
I've seen people replace the internals on these.
If it's a 5 door, the entire seat can be taken out quite easily and there's few moving parts so I would just check all of the retaining bolts are secure.
Other things around that could be the leather arm rest rubbing off it or the seatbelt holder rubbing off you. Often other surrounding items echoing off the internals can sound like other things.