This is normal, those noises will start when you exit a channel and the 'wii squares' appear, i think its just the wii checking for the disc so it can display the game on the wii menu.
Dont worry :thumbsup:
Lee.J
Maybe because your wii is over-heating? You should feel/check your wii the next time you play a game for a while, if it is over-heating, place it in a cooler area. If the problem still persists, contact Nintendo
Lee.j