I've never really seen a movie or television show with a character that gave me trans vibes, but there are a couple of characters where I can envision an alternate universe wherein said character was transgender. It's an interesting thought experiment. I think I would view my life and my history very differently if I had been cis, so it's kind of fun/challenging to think up all the ways in which being transgender would impact a character.
EDIT: I guess I'll use Iron Man as an example (as inspired by my icon, haha). Since Tony Stark is a public figure, his transition would be pretty big news. We know he was born male, but in an alternate universe in which he was a trans man, how could he pull it off? Probably Antonia Stark would have to die with "her" parents, leaving a "cousin" to step up as the Stark heir. A lot of Iron Man has to do with performative masculinity and father/son expectations -- something which would probably impact an FtM Tony Stark quite a lot. And then there's the sex stuff! Hard to be an international playboy when you're living stealth and any insider scoop could earn your hookup millions on the gossip market. So much of his life would have to be razzle-dazzle smoke and mirrors.
Imagining a universe where Tony Stark was a closeted trans woman is interesting too. What would she do with all that spotlight? Could some of the "flash" of Iron Man be read as overcompensation? How would her relationships change? I guess I can look to Caitlin Jenner as an example! Etc etc etc.
So it's kind of a fun game. Not really a "headcanon" though. Guess I didn't answer your question, sorry!