Why does my cursor jump when typing?

Changing the cursor theme back to the default Adwaita (theme) in My Unity resolved this along with lowering the pointer speed and sensitivity in system settings >> mouse and touch-pad

This problem was driving me bonkers too. Finally I went to the Ubuntu Software Center, entered "touchpad" in the search box, found "Synaptiks" touchpad manager and installed it. Set it to start up at boot. Set it to lock touchpad when typing and set the delay time to 2 seconds. My problem is gone. It was so bad that I was looking for a non Ubuntu based distribution to replace the Ubuntu OS I have been using. Now I am very happy again. The old touchpad manager was supposedly sat to lock the touchpad when typing but it really was not. Good luck.