undo cursor position
> Does exist a command to undo the last cursor movement and come^O is the fast/easy answer.
> back to previous position?
Vim maintains a "jump list" of recent jumps. You can use ^O and
^I (that's control + "oh" and "eye", not "zero", "one" or "ell").
Small movements don't update the jump list, but large movements do.
See ":help jumplist" and ":help jump-motions" for more details.