Fix it with a few easy steps. I noticed yesterday my Note 4 was having relatively poor battery life the last few days so I did a wipe cache partition.

Here is how you do it.

Turn off your phone
Press Power, Volume Up and Home simultaneously
Wait until the phone vibrates and then release Power and Home
You should now see the recovery screen. Use the volume buttons to move and select Wipe Cache Partition.
Press the Power button to confirm.
Select Reboot System Now and again, hit Power to confirm.
Wait until your Galaxy phone reboots and hope it’s fixed the problem.

Also I've noticed it will speed up my phone.