Are you using a laptop or a desktop?

laptop.....

Are you maybe accidentally touching the touch pad as you type?

Accidental grazing of the touchpad on a laptop while typing is the most common way that people get problems like this. I had the problem of the cursor jumping around as I typed and causing changes in my text in the wrong places. You have a number of options regarding disabling the touchpad. I tend to prefer a wireless mouse instead of a touchpad on a laptop, and my laptop is set up so that the touchpad is automatically disabled any time the mouse is functioning. If you need instructions on how to disable your touchpad, tell us what your operating system is and if you intend to use a mouse.

It only did it one night...hopefully not another session like that! It is possible that I touched the keypad as I don't feel my fingertips, but I would think that it would happen more often, every time I use the computer.It would change pages about once a minute. I turned it off that night and it hasn't done it since.