It could be a vocal tic and not a stim.
I had a throat-clearing tic (it's called tic, not tick) around ages 11-12/13. I didn't do it intentionally but couldn't not clear my throat, no matter how hard I tried to stop it. I remember that at that age, I felt uncomfortable and "edgy" when I tried to hold it back for a few seconds and I felt much better, less tense and edgy, only when I finally cleared my throat. That's how I felt about it back then anyway when I didn't yet know what this frequent throat-clearing was about.
I'm not sure how many people with a form of autism have tics but I know that a lot kids and adults with ADHD develop tics at some point. For a lot of them, the tics decease in number and "vanish" later on but some people have tics such as throat-clearing or shoulder jerks into adulthood.
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Autism + ADHD
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The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it. Terry Pratchett