My Wii has a temperamental problem reading discs.
It accepts the disc fine, but then the system doesn't recognise that a disc is actually in. To get it to work, I have to tilt the Wii to the side, which usually makes it work.
When it does work, there is sort of a heavy click sound and then it runs fine.
However this is not always the case and sometimes it works fine. But I've noticed it's getting worse.