Sounds like the throwout bearing rattling??? I have had this same prob with the sachs throwout bearing that came with my clutch when I bought it. It rattles, and if you engage/then disengage the clutch just right while sitting still...it settles it. I wouldn't worry about it..I've driven over a year with it like that, and my prob is def. the bearing. Maybe there's another one made with tighter tolerances. Just my thoughts.