Curser jumps to another line while typing

I have a reoccurring problem when typing emails or documents. I can be composing and all of a sudden, the cursor will shift to several lines above and begin entering the letters I am typing. I also can generate a "Highlight" line, which if I'm not paying attention, will delete that line. Very frustrating to say in the least.

Anyone help? Seems like a keyboard problem, but cannot characterize it.

A proposed solution to this problem was to go to Trackpad in preferences and deselect "Tap to click" Mine was already deselected. Terry