I just set up a new galaxy S6. At one point the notifications would pop up with a sound and a notice in the screen of the event. It would only send a notification for texts, emails, and weather emergencies. Somehow during setup the notification went into overdrive and will make the notification sound every few minute or so without a pop up on the display telling me why the notification sounded. I turned off notification in each app and I had turned on notification in Google+. Notifications still goes off every few minutes without any explanation as to why it is notifying me. My only way to not handle this is to turn down the volume on notifications to 0 to prevent the notification sound going off too often.