Synonyms for Instinctual:

adj.

instinctive (adjective)
intuitive, visceral.
intuitive (adjective)
crafty, canny, cunning, tricky, astute, clever, shrewd, artful, sophisticated, intuitive, far-sighted, sly, instinctive, insightful, wily.

n.

thoughts, by accident, random, accidental, arbitrary, impromptu, unintended, coincidental, visceral.

Other synonyms:

visceral. Other relevant words:
unintended, random, accidental, thoughts, arbitrary, coincidental, visceral, impromptu.