That is courtship, not illness, and your instinct that it does not look like illness is correct. Parrots feed their mates and chicks by bringing food up, so a bonded pet lovebird does it for whatever it has bonded to: a cage mate, a mirror, a favourite toy, or you.
The tells are all in your description. Deliberate, head bobbing and pumping, calm and focused, food offered rather than flung, and a bird that is otherwise healthy and busy.