If your Nexus 7 tablet is getting locked up and becomes unresponsive for some unknown reason, you can restart the tablet fairly to fix the issues. That don't erase any data and apps. It just shut down the device and boot it back up again.
How to restart locked up Nexus 7
* Pressing and holding the power button for about 10 seconds. The display screen go black and show the Google logo. Thne you will get into normal mode.