Sorry, I'm not intimately familiar with the S5's settings to know if there is an option to change that. Let me ask someone else. Did that happen after a system update?
OK, try the following:
1) Disable the lockscreen. Turn screen off, then on. Then re-enable it.
2) Same thing for lockscreen notifications. Disable them. Screen off and on. Then re-enable them.
Power down your phone, now press & hold the power button, volume up & the home button until your phone boots into Recovery. Now use the volume rocker to select Wipe Cache. Hit the power button to make it happen - give it a sec to clear the cache. Now use the volume rocker to select Reboot System - hit the power button & run you phone for a bit. See if this helps