Cursor problems

I am running Lubuntu Bionic Beaver 18.04 on an old Toshiba laptop. It has been running well, but now I have a problem with the mouse cursor, it slides off the screen and hides, if I leave the cursor in the middle of the screen on the desktop,it will slowly slide down to the left hand corner of the screen and hide, I can eventually retrieve it, but I can’t figure out why it is doing it, I am using the notebook touchpad. Help please!