The cursor jumps around on my E-105-S1402,

Yes.
Most probably, you are involuntarily very lightly touching the surface of your touchpad with the base of your (usually right) thumb.
Some touchpad drivers have special settings to ignore very light strokes to avoid this effect - try your pointing device settings in the control panel.
If yours doesn't, you just have to remember to keep your hands at such an angle as to avoid contact with the touchpad. A soft wristrest may help, as it elevates your wrists a bit; gel-type wrist support is my favorite.
Good luck :)