i have done some searching and have seen many others with this issue, although it seems for others it happens after the red netflix screen comes up and then it freezes.
for me, i just finished watching a star wars bluray, hit the PS middle button, letf it still runnign basically, then hit netflix and nothing moved, the screen was froze on the home area and there was this horrible "rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr" sound. like a fan was in overdrive...?
buttons did nothing, i couldnt turn on the controller to do anything so i had to unplug it and after a reboot it did a HDD scan. no errors came up, and then it scolded me for unplugging before powering down, lol.
after that everything seemed OK. i just turned it off again cause im a lil paranoid. i had a ps4 die on me last year in the middle of playing DAI, it was the first console to ever die on me and i have had many.
so, if anyone knows anythign else about this, or have had this happen to you, would love to know what happened and if your PS4 has been ok since.
thanks, cheers.