Settings > Connections > WiFi > (menu soft button) Advanced
Uncheck 'Always Allow Scanning' (5th item down on Advanced settings page).
Go back to Home screen, long-hold power button, and select 'Restart' from the dialog box that appears.
Hopefully this will resolve the problem for you. The 'Always Allow Scanning' advanced setting under WiFi isn't really necessary and can cause boot loop issues. My Note 3 began doing this and removing the external SD card would stop the boot loop from occurring, thus leading me to assume the problem was related to the SD card is some way. This turned out to not be the case.