That is very odd. Are you sure there isn't an app that is causing your issue, or malware or a virus? Any of those could cause this problem. You might want to try starting up the device in "Safe Mode" and see if the problem happens then. Granted you will have restricted access while in it, but if the problem doesn't show while you are, then you know it is something on the device (app, malware, virus, etc.,) that is the cause and you would need to remove whatever it is 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.