I have this same issue and it started just about the same time as the original post on this thread (mid January 2019). I had this laptop since September 2018. It usually happens every 3-4 days, not every time the screen turns off or is in sleep mode. When I want to wake the system by either pressing any key on the keyboard or pressing the power button, the keyboard backlight comes on but the screen remains black. There is nothing I can do other than force shutting down by holding the power button.

I chatted with a Dell support agent online, they tried changing settings through remote access and switching some Power Plan settings but the problem remains. I have all the latest drivers and BIOS version 1.8.1. The Dell support agent and I have been emailing back and forth over the last few days. They said , "We do not have any such known issue with the system." and wanted me to put computer into Safe Mode to see if it still occurs, but I don't want to remain in Safe Mode for a few days since the issue doesn't occur every time it Sleeps. The agent then told me to disable Hibernate Mode, which I did but once again about a day later the computer wouldn't wake, just black screen. And now today I received an email from Dell support telling me to reinstall Windows 10. I am not going to spend all that time backing everything up and reinstalling.

I read on a forum of someone with the same problem say that it happens on systems with Intel and Nvidia GPU's as it switches to the Intel display and fails. Not sure if that is the true problem for this though.

It sure is annoying when the screen is black and you had things open unsaved. It's not a good feeling when every time I go to use my expensive laptop I expect it to not come on. Please find a fix for this Dell!