Try starting up in "Safe Mode" and see if it will load. If it does, then you have something on the phone that is interfering. Bad app, malware, virus, etc. that you will need to remove. Also, while in "Safe Mode" I would suggest connecting to a computer or other device that you can move your files to (not apps) and save them off the phone this way if you need to do a "Hard Reset" or even get it repaired you won't lose anything.
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.