not a new problem with older devices . I think it's screen flickering which you want to mention here it's actually happens sometimes with older amoled displays ! nothing to really worried about but I suggest you to contact your nearest service center once . one suggestion form me _ do a backup with you on your Samsung cloud ☁️ if by any chance your display stopped working you can restore all your contents on an other Samsung device .
Please perform the below mentioned steps to resolve the issue:
* Check device in safe mode: Press and hold the Power key, when Power off icon appears > Press and hold the power off icon. To exit safe mode: Restart your device.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
