Involuntary Body Reactions to Happiness

It's a stim! There are all kinds of different stims for different feelings. I also wiggle when I'm happy, I chew on things and make popping sounds with my mouth when I need something like food or sleep, I fidget with things in my hands or sometimes chew when I'm focusing, and I hit myself in the chest when I'm anxious or frustrated although I'm working on redirecting that into a less harmful stim (rocking and rubbing my arms). Stims can be almost anything and can range from harmless things that people might even consider cute or endearing to things that are disruptive or destructive and could get people including the stimmer hurt. Also while it is an important and relatively common self soothing activity for autistic people and neurodivergent people in general it is also something that neurotypical people do on occasion as well when they need self regulation.

I wiggle as well, and sometimes, make this high pitched hum. (⁠✿⁠^⁠‿⁠^⁠)

I wiggle in my chair when I eat something I really enjoy lol so, I exaggerate it and embrace it 💕

That's called stimming! While it can get you looks, it's something to enjoy! It's a unique way of emotional release and different for everyone🤗 I stim when I am upset.