I began having this issues on my iPhone 7 following the iOS 11 update. I reset the phone and set up as new. Nothing. Took the phone into apple countless times. They reinstalled 11, reset the phone again as new. Nothing. They gave me a brand new 7. Same thing. All the same steps again. I decided to upgrade to the 8 figuring that would get rid of the issue. After all, the 8 came installed with iOS 11... Set it up as new.. SAME THING. Take it back in. They swapped it out for another new 8. Mind you, it cost me money to upgrade in terms of new applecare and tax, for a phone I really didn't want as I was happy with my 7 and planned to own it in a year. I get a call back from applecare and they escalate it to engineering. They ask for a diagnostic and screenshot of the blank screen, and I provide it. The woman was very helpful at first, now she won't return my calls...
Nothing works for this issue. I thought possibly I had a corrupt file in the cloud, however, I have no problem with my iPad Air 2 running iOS 11.0.3 (same as my phone) and I have everything synced. So that's not it. Thought it was a horoscope website I started using. Cleared my Safari history and it stayed away for 8 days (!!!) before happening again. NOTHING WORKS to keep this horrible bug from returning.