When I was cleaning my glock 23 (.40 cal)....?

When I was cleaning my glock 23 (.40 cal) I shook it a little and hear a rattling noise, when I ****** it and shook it there was no rattling noise. should there be any rattling at all ? it has progressively gotten worse and now its a big rattle(after other shooting and cleaning)....is this normal? Can I make it not rattle? I think its the firing pin, but I dont know ....any help? Thanks