Could be. Flapping or shaking one hand is a stim for me, something I do when overly nervous or stressed. My two year old vocalizes non-words repetitively when under/overstimulated. My daughter squeaks or repeats a word or phrase, or sometimes spins. I think stims can be pretty much anything, depending on the person, the reason and the need.
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Curiosity is not a mental illness.
Homeschooling Aspie mom of 2 kiddos on the Spectrum.