I have been seeing reports all over of the new iPhones not charging unless the screen is turned on, and in fact that is what the iOS 12.0.1 update purported to fix, but my iPhone X has not charged unless I unlock it since I got it. It will charge wireless while the screen is off, but if I plug it in, I need to unlock it or I don’t get any charge. And yes I have tried 6 different cables and I have the issue with any cable and different chargers or my MacPro 5,1.
This is super frustrating and in fact I have had quite a few days where I go to use my phone and it is almost dead though was plugged in all night.