Try turning it off and then starting it up in "Safe Mode" and see if it will load. If it does, while you will have limited access, that will also tell you that there is something interfering on the device. Bad app, virus, malware, etc., which you will need to remove before it can run normally. If it won't even load in "Safe Mode" then you may well need to either "Hard Reset" it (which would wipe all data) or have it looked at for a hardware issue.
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.