If Star Trekkin'
counts, then that was my first experience of Trek.
Otherwise it was watching TAS as part of my Saturday morning cartoon line-up. I enjoyed it, but it wasn't what made me a fan of the show. That didn't happen until I started watching TNG around '91 or '92. Then one summer Sky started running TOS when they ran out of TNG, so I watched that and was surprised to find it enjoyable, too.