Yesterday, I used my phone as normal and went to use it and the screen was black, unresponsive and the bottom quarter f the screen flashed white occasionally. Nothing I tried would turn it on, not charging it more and not holding down the volume-down and power buttons. I couldn't turn it off or on. When I tried plugging it in to my laptop, he laptop beeped to indicate it recognized a source connected, but the Phone drive wouldn't show on the pic and still nothing showed on the phone screen. We tried finding a message with a similar problem/description online and did, but can't open the messages read how things were resolved, so I'm adding my own message here. I left it last night, intending to let it wear out the battery maybe, but my morning alarm woke me up from the phone, so there are still programs running on the phone, which is positive/makes me hopeful.
My last phone was a Galaxy Note4 which I babied and had for a few years, and it just went black and never recovered, so I'm anxious I will lose valuable data. Hope I can receive guidance to get this phone back in working condition. Thanks for any support offered!
My galaxy note 8 did that. It randomly started flashing black and white and sometimes green and red. I could turn it on, but I couldn't see anything. Wound up being my LCD screen had gone out. I was able to get it fixed and it's been fine ever since. I'm certainly no expert but your situation sounds similar to mine, so it could just be that. Good luck!