Try starting it up in "Safe Mode" and see if it works fine. You won't be able to access many apps, it prevents that, but you will be able to access some things. If the phone doesn't freeze up, then you know there is something software related. Bad app, virus, malware, etc., that you need to remove from the device. If, however, it still freezes up even in "Safe Mode" then I would have it looked at as it may have hardware issues.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.