Bright or reflected light may be interfering with your Leap Motion device.
The Leap Motion controller works by using an infra-red camera to detect your hands and their movement. Sometimes this camera can be disrupted by bright or reflected light and cause hands to make unwanted movements in the headset. To solve this issue, try facing away from bright lights, rolling up your sleeves, or removing jewelry on your arms. If the issue persists, try restarting the computer.
Note: In some machines, a small amount of hand movement is normal when running Group Mode.