A. Try restarting it. That may resolve the issue.
B. If restarting doesn't work, try shutting it down and starting it up in "Safe Mode" and see if it will stop scrolling. If it does stop, then you may have a bad app, virus, malware, etc. You would need to find and remove the problem then restart the phone again.
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.
If it actually does still happen in "Safe Mode" you may have to do a "Hard Reset" of the device, or if that doesn't help, it then could be a hardware problem.