My lock screen turn grey ... it gets normal after restart
- Are you using a custom theme?
- Installed any apps?
- Check the lock screen wallpaper
Try this as well:
Wipe cache partition
1) Turn off the device.
2) Press and hold the Volume Up key and the Bixby / Power key.
3) When the Android logo displays, release both keys.
4) An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5) Press the Volume down key several times to highlight wipe cache partition.
6) Press Bixby / Power key to select.
7) Press the Volume down key to highlight yes, them and press the Bixby / Power key to select.
8) When the wipe cache partition is complete, Reboot system now is highlighted.
9) Press the Bixby / Power key to restart the device.