On our works Dell laptops we used to get that problem.
The engineers explained to me that the ribbon cable going to the "nipple" mouse in the center of the keyboard wasn't sufficiently electrically shielded, so it could pick up interferance which moved the pointer.
The long term fix was to upgrade the ribbon cable - Dell had started using better shielded cables. But the short term fix was simply to go into Control Panel and disable the "nipple" mouse.
RC