Two-Finger Scroll Disables--Inspiron i3148

Pretty new machine. Works well but this is annoying. About every other day, without anything special happening as far as I can tell, the two-finger scroll disappears. I have to turn machine off and on to restore. I don't know what I'm doing to turn it off, and I'd like to know if there's a way to turn it back on without shutting down.

Thanks