Nexus 7: How to Restart Locked Tablet
Every now and again, your Google Nexus 7 tablet by Asus is bound to get locked up and become unresponsive. If that happens, you can restart the device fairly easily.
Restarting the device won’t erase any data, it will just shut down the tablet and boot it back up again. Since you can’t access the battery on the tablet, you restart it with button presses.
To restart the tablet, simply press and hold the power button for about 8 to 10 seconds. The screen will go black, and then you’ll see the Google logo again, and the tablet will boot back up like normal.