Cause
The noisiest piece of equipment within the Wii console is the fan that keeps the system cool. As the system begins to heat up, the fan runs faster, and this movement will cause the system to vibrate.
Function
As the Wii reads games, it spins the disc in the drive while a laser reads the data. This spinning can be quite fast and can lead to the small console shaking while reading games.
Uses
The Wii is also compatible with Gamecube games and controllers. Because of the size of Gamecube discs and the need for wired controllers, the hardware performs differently, which can cause additional vibration or noise.
Prevention/Solution
You can prevent the amount of vibrating by placing the Wii in a horizontal position. This will cause less movement of the console during play.
Warning
If your console continuously vibrates violently or makes extremely loud noises, it may be overheating or need a replacement drive. Contact Nintendo for service.