Hi
Have you tried reseating and cleaning the trackpad connection on the logicboard
Here’s the guide you will need
[guide|139747|new_window=true]
Also have you tried a wired or wireless mouse to see if the behaviour persists?
If a different mouse works fine and reseating it doesn’t work it could mean that the trackpad or the cable is faulty and needs replacing
It could be a logic board issue but that is quite unlikely but not off the table
Hopefully this helps
Any questions please ask
Thanks:-)