Try the following and if it is still there then it's a hardware issue.
Clear all cached data from the phone and check.
Try a factory reset and check.
Be aware that a factory reset will erase all your data and downloaded apps from the phone. It will restore the phone to its factory default condition. Backup the phone to the cloud or a computer before performing the reset. Also if the phone has a Google or Samsung account associated with it, you will need to know the user ID and password for the account so that you can enter the phone after the reset due to the FRP lock ( factory reset protection) being enabled by the reset.
Once the phone has been reset check if it works OK.
If it still doesn't work OK its a hardware problem.
If it does then restore the phone with the backup you made earlier using the phone's Restore feature (found in Settings). Once it has been restored to what it was, check if it still works OK.
Does it do this when using the phone in safe mode?
Yes it happens in Safe Mode. All I need to do is shut off the screen by tapping the power button or let the screen time out, then tap the power button or the Home button to wake it back up. If it hasn't been asleep for at least 30 seconds, the screen comes back on but is unreadable and doesn't respond to touches. My only recourse is to tap the power button to put it to sleep again, which shuts off the screen, then wait about a minute to try again. Usually if it's been asleep for over a minute the screen will come up normally when I wake it up.
by Tom Hudson
Does the screen become unreadable or unresponsive when you just tap the phone at various places i.e. back, sides etc
Just trying to work out if it may be a loose video flex cable connection.
Has the phone been dropped or gotten wet at all?
@jayeff I've tried tapping around a bit to check for loose connections -- no responses. I've tried tapping it a bit when this happens to see if the display will change or come back -- there is no visible change to the display, so I don't think anything is really loose. Phone has never been dropped -- it also has a silicone case so it never really gets jarred at all. It looks brand new. It hasn't gotten wet, either.
I have to wonder if it's some sort of electrical issue; like maybe when the screen is turned off a capacitor needs to drain before it is turned on again.
by Tom Hudson
Here is a short video showing the problem. You can see that it initially looks fine; this was when I turned it on after it had been off for several minutes. If I wake it up right after the screen times out or it is put to sleep, you get this bad display. Maybe this will help someone diagnose what is going on here. I like this phone and don't really want a new one; would like to be able to fix it if possible. Thanks for any input. https://youtu.be/h8igPvYUB9s
by Tom Hudson
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