I have had two black screens on boot requiring a hard restart after shutdown just recently (one of those it looks like it didn't shut down correctly as it was both hot and the camera light was on when I opened the cover when I got home though the screen was black).
Experienced this a couple of times. Perform a shut down and put in bag. On removing several hours later, machine is very hot (so still powered on) but black screen - can't wake it from sleep and it won't respond to power on. Hard reset required to get back on track.
With the Surface Pro 4 - long press of the power button while pressing volume up is the friend you get to know, again, and again, and again ....
Memo to Microsoft. When designing the Surface Pro 5, the addition of a LED power indicator light would be really really really useful!