On the SHIELD TV Home
screen, select Settings 
.
Under "Device," select Screen saver.
Select When to start.
Select one of the options.
SHIELD TV will automatically go to sleep after the time period:
On the SHIELD TV Home
screen, select Settings .
Under "Device," select Screen saver.
Select When to start.
Select one of the options.
To restart:
On the SHIELD TV settings, select "Restart"
If this is unsuccessful, you can also unplug the power cord, wait 10 seconds, and then plug the power cord back in.