I think there may be a software glitch for some mostly with the keyboard and YouTube that may get fixed by some Apple update.
But in most cases it's a hardware problem, especially on Pros (including 2017 and 2018) but minis and regulars are affected too. Here are more threads on the problem:
https://forums.macrumors.com/threads/irresponsive-screen-ipad-pro-12-9-2nd-gen.2121051/
https://forums.macrumors.com/threads/2016-ipad-pro-12-9-screen-intermittently-unresponsive.2118824/
https://forums.macrumors.com/threads/12-9-ipad-pro-gen-3-touchscreen-problem.2154220/
https://forums.macrumors.com/threads/ipad-pro-stuttering-issue-now-more-widespread.2165593/
https://forums.macrumors.com/threads/missing-keystrokes.2166241/
https://forums.macrumors.com/threads/known-problem.2168160/
https://forums.macrumors.com/threads/10-5-pro-with-unresponsive-screen.2170164/
https://forums.macrumors.com/threads/2nd-gen-10-5”-degraded-touch-screen-sensitivity.2172781/
https://forums.macrumors.com/threads/ipad-pro-12-9-2018-screen-latency-issues.2173735/
https://forums.macrumors.com/threads/screen-stutter-ipad-pro-2018.2161383/
https://forums.macrumors.com/threads/screen-touch-unresponsive-on-2018-ipad-pros.2176116/
https://forums.macrumors.com/threads/screen-stuttering-issue-on-11-ipad-pros.2176379/#post-27268554
Also a long thread on ifixit where people try numerous software solutions that in the end never help:
https://www.ifixit.com/Answers/View...ouchscreen+is+unresponsive+from+time+to+timeh
In most cases it's hardware problem that cannot be fixed by simply resetting, pressing buttons or updating. It should be fixed by Apple on their manufacturing side.
But in most cases it's a hardware problem, especially on Pros (including 2017 and 2018) but minis and regulars are affected too. Here are more threads on the problem:
https://forums.macrumors.com/threads/irresponsive-screen-ipad-pro-12-9-2nd-gen.2121051/
https://forums.macrumors.com/threads/2016-ipad-pro-12-9-screen-intermittently-unresponsive.2118824/
https://forums.macrumors.com/threads/12-9-ipad-pro-gen-3-touchscreen-problem.2154220/
https://forums.macrumors.com/threads/ipad-pro-stuttering-issue-now-more-widespread.2165593/
https://forums.macrumors.com/threads/missing-keystrokes.2166241/
https://forums.macrumors.com/threads/known-problem.2168160/
https://forums.macrumors.com/threads/10-5-pro-with-unresponsive-screen.2170164/
https://forums.macrumors.com/threads/2nd-gen-10-5”-degraded-touch-screen-sensitivity.2172781/
https://forums.macrumors.com/threads/ipad-pro-12-9-2018-screen-latency-issues.2173735/
https://forums.macrumors.com/threads/screen-stutter-ipad-pro-2018.2161383/
https://forums.macrumors.com/threads/screen-touch-unresponsive-on-2018-ipad-pros.2176116/
https://forums.macrumors.com/threads/screen-stuttering-issue-on-11-ipad-pros.2176379/#post-27268554
Also a long thread on ifixit where people try numerous software solutions that in the end never help:
https://www.ifixit.com/Answers/View...ouchscreen+is+unresponsive+from+time+to+timeh
In most cases it's hardware problem that cannot be fixed by simply resetting, pressing buttons or updating. It should be fixed by Apple on their manufacturing side.