If you can track it down to certain cd's that are vibrating, try them in a different player, maybe it's the Oppo that is the problem. I'm not sure a slight warp would cause a vibration, it may be more likely an off center (out of balance) disc can cause a vibration, those discs can be cut to even them out. I only own several hundred cd's but have never seen this problem, good luck tracking it down.
Mike
Mike