I had the same problem, so I followed Nintendo's advice, and it worked. Here's the excerpt below:
Quick tip: Cursor (hand) or character movement not responding properly?
Hold the Wii Remote with the button side down. Without using much force, firmly tap the button side of the remote against the palm of your other hand a few times. Doing this does not take a lot of force, so be sure not to tap the Wii Remote very hard. Check for proper response. If the problem is not solved, please follow the rest of the instructions on this page.
I some times have this issue, but it's down to a reflection from a window either on the sensor or mote.
I just close the blind that is causing the problem and it solves it.
I also have 3 motes 1 I got with it, 1 bought from a local shop and 1 I bought on ebay from china, this one is very sensitive and I don't use it much because it always flickers and adjusting the sensitivity of it thoughs off the others.
It would be great if you could adjust the sensitivity for each mote, but you cannot. So I have to live with it.
Try another mote if you have one, adjust your sensitivity and make sure there is nothing interfering with the sensor bar or inferred mote