Hey @reirei, no fear needed here! As fellow member @dragonbait has already mentioned, it's due to the camera. The device supports a high speed shutter function that automatically focuses the camera. The sound you hear is the camera lens shutter moving inside the barrel and it's a normal sound. When you turn the camera on the sound will stop as it is actively focusing. Sometimes the device makes this sound when you vibrate or lightly shake the device. :)
mine does it also I noticed something the other day when I set the phone down and it almost feel off the table but I caught it, that's when it rattled.i will continue to monitor it to see if it gets worse.
