If it is hardware there is nothing I can do other than suggest you take it in to have it repaired.
If it is software, then you should be able to try starting it up in "Safe Mode" and see if it will load. While in that mode it would give limited access, but if it does load, then it is a something on the device causing the issues. Bad app, malware, virus, etc. If it won't load in that mode, then I would think hardware.
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.