Recently, I started receiving audible Notification alerts every 3 minutes from a yet-to-be determined source. Although the sound, indeed, is the app notification sound I set, it is not associated with an app which i established an association. Even when I block alert notifications for all of my apps, the recurring alerts still occur. I'd appreciate any help that would lead to the cessation of these unwanted and irksome alerts. Thank you.
Can you try using your phone in safe mode? To do this, turn off the phone > After a few seconds, turn on the phone > When the Samsung logo displays, press and hold the Volume down key until the lock screen displays. When the lock screen displays Safe mode will be shown in the lower-left corner of the screen.
Please monitor this for a few hours and let us know if the notifications stop. If they do, this would indicate that a third party app is causing the issue and you would need to uninstall recently downloaded apps individually, to find the culprit. To exit Safe mode press the Power/Lock key and then touch Restart.