They say it's from the low temperature of your room.
When the device is not turned on for a long time in a low temperature, some parts inside LED display shrink.
And when the device is turned on, you hear expending sounds.
I, for one, think that's crap that I have to hear it.
$900 display, and you hear clicking noise at startup.
But I do only notice it when my display is turned off for a long time in a low temperature. After I use it for awhile and the display returns to the room temperature and gets warm, I don't hear the clicking noise anymore.
So...