Try starting up in "Safe Mode" and see if it will fully load. It will only have limited access in that mode, however if it loads then you know there is something on the device that is causing your issue. A bad app, malware, virus, etc. that you will need to remove to resolve the problem.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
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.