I don't know if there was a clearly defined "starting point" because, from before my earliest memory. I always felt I WAS a girl and tried very hard to resist being pushed in a male direction as early as age 5 (my first encounter with gendered washrooms). I always had a wardrobe that included at least some feminine items. By age 13 or 14 I had two wardrobes - one male-ish and one feminine - and lived partially en femme (whenever I could get away with it). By my latter teens, I lived mostly unisex or straight-out female.
There was no legal way to 'transition' in those days (1950s & 1960s) so I didn't fully transition until surgery became available in 1974. At that point, transition was like flipping a switch.
