I have seen many users report this issue as well in reddit after installing one ui 5.0. The screen flickering too often (could be related to adaptive motion where it flicks when the screen detected a move after it sits for awhile, it also constantly flicks when open notification bar or quick setting), its getting annoying and is making the user experience getting worse day by day. I am really pissed at the phone level of quality from one of the largest corporate firm in the world.
I really hope Samsung can fix this problem as it should NEVER HAPPEN in a phone that cost more than $1000 US Dollar. Please fix this issue in the next update, thank you and appreciate it.