It could also be that some of your discs are warped, causing them to hit the sides while playing. This tends to happen to discs that are used or left in the car system for a long period of time.
DVD Spinning noise normal?
I had a cheap Toshiba DVD which had spinning platter noise noticeable on quiet passages. I bought a used Sony DVD S7000 high end player which does the same thing but not on all disc's.The original owner stated he noticed it also but only on some DVD's. Any reasons why DVD players are super quiet like high end CD players? Thanks