Most of the time when I hear symptoms such as these, the computer turns out to be a laptop computer and the cause of the cursor jumping around is because when you type on a laptop computer your wrists or palm of your hand ends up brushing close to the touchpad, causing the cursor to jump around the screen. If you have a laptop but use a mouse, try disabling the touchpad. On some laptop models, this is done by double-tapping a small LED in the upper-left corner of the keypad. Otherwise, check your control panel or device manager.
HTH,
JW