I had the same problem with a frozen screen on my Galaxy Tab 4 7.0 Nook..... what caught my attention to the issue is that I heard a sound like a truck idling outside. I had the sound turned down so it took a while to notice. Holding the power button (a little longer than 10 seconds) finally did the trick and it rebooted automatically. Problem is, this is not the first time I have heard the same sound. When it happened a week ago and I realized there were no trucks idling outside my window, I figured out it was my tablet quickly turned off the tablet and left it alone until the next day. I'm concerned about the sound more than the frozen tablet. Is that a sign that it's about to die? Has anyone else heard this sound too when their tablet froze?