Johnny Manziel -- Hands Off MY Girl

Johnny Manziel looks like he's ready to hang up his chick-chasing cleats -- and he and his GF let everyone know it this weekend with an Instagram that's either totally romantic, or borderline stalker-ish.

Smoke show Colleen Crowley posted a pic of herself pretending to kiss a screen showing Johnny's news conference after his first NFL preseason game -- which you'd expect. He's Johnny Football, after all.

So, is Johnny getting serious enough to strap himself to one chick ... just as he's on the verge of NFL stardom?