Hi NP,
It sounds like something on the system may be continuously sending pointer input, which can cause the cursor to move or click on its own. Since you've already disabled the touchscreen in the past, it may be worth checking other built-in input devices as well.
Here are a few additional steps that you can try:
1, Disable the touchpad temporarily
- Open Device Manager
- Expand Mice and other pointing devices
- Right-click the touchpad device and select Disable device
- Test with only the external mouse connected
2, Perform a Clean Boot
- Press Windows + R, type
msconfig - On the Services tab, select Hide all Microsoft services and click Disable all
- Restart the PC and check whether the behavior continues
3, Check for accessibility features
- Go to Settings > Ease of Access
- Review Mouse, Touchpad, and Tablet-related options and disable anything that may control pointer behavior automatically
4, Reinstall the touchpad or HID driver
- In Device Manager, uninstall the touchpad or HID-compliant pointing device
- Restart Windows and allow the driver to reinstall automatically
If the issue persists even with the touchpad disabled and after a clean boot, that may help narrow the cause to a specific driver or hardware component.