This used to happen at work, on our Dell laptops.
The problem was the little mouse button (alternative to external mouse or touch pad) between the 'G' and 'H' keys.
In fact the exact problem was that the cable going to the little mouse button didn't have sufficient electrical shielding, and sometimes it would pick up electrical interference from the rest of the laptop and go haywire, sending the mouse pointer all over the screen.
Short term fix; disable the little mouse button in "Mouse Options".
Long term fix; call IT and get an engineer to fit a replacement keyboard - later units had an upgraded cable with better shielding.
RC