Galaxy S5 notification sound, without a notification.

[AC Question]

For the past 4 or 5 days, my S5 has been, only when connected to wifi or 3/4G, playing my notification sound but not showing any new notifications. I should add that this seems to be in addition to text, Snapchat, or Facebook notifications that I still get. Could it be possible that there is an app that isn't able to show a notification, like if it were to be turned off in that apps settings? Or is there something else wrong with my phone?
Any help would be appreciated, Thanks.

 

[B. Diddy]

Yahoo Mail is a common culprit. Otherwise, try wiping the cache partition: Reset: Samsung Galaxy S 5 | T-Mobile Support