Hi Delta, welcome to LF!
Ok, so I'm assuming that this is a constant problem and it isn't something that happens for one second and then goes away. Is that true? If it's only for a second, I wouldn't worry to much about it.
So I searched through the Internet to see if I could find something, like a similar problem... Nothing, of course.
My guess is, your cd is the problem. Try cleaning it, and if that doesn't work I don't know.
Sorry if I was no help. Good luck fixing it though.