|Have you, or is it possible anyone else has....|
- dropped this computer, or dropped anything on it, or subjected it to a physical jolt otherwise ?
- spilled liquid on it, or exposed it to liquid such as rain, or sprayed it with liquid ?
Has there been a power failure event while the computer was plugged into the AC adapter ?
A nearby lightning strike ?
Try an external mouse.
If that works fine, either there is a loose connection to the touchpad inside the case , or you need to replace the touchpad. Replacement touchpads are a frequent replacement item, easy to find on the web, and not all that expensive.