Make sure you're not touching the screen when the phone vibrates.
Auto launching the camera with Motion Launch Snap
When the screen is off, you can wake up the phone directly to the Camera app.
§ Press and hold the VOLUME UP or VOLUME DOWN button, and then lift the
phone in landscape orientation.
§ Or first lift the phone in landscape orientation, and then press the VOLUME
UP or VOLUME DOWN button right away.
76 Your first week with your new phone