Stipulations:
- You cannot die and are immune to disease
- You cannot alter the future such that you change the world from your point of origin. i.e. You cannot become so famous that future people recognize you as immortal.
- If you vary the timeline too much you will cease to exist.
Functionally impossible unless you completely isolated yourself from civilization. Any impact to “the past” will alter your origin, even if just by changing which sperm cell fertilizes a complete stranger’s child. You have to define what “too much” variance means.
Had to scroll too far for this :)