It's hard to keep track of it if you've always done it.
But I do it every now and then and it's probable that I'm on the spectrum.
When I'm alone at home, I do many different things like say random sentences, repetition of words or sounds. I like to sing to myself from time to time. I especially do this when I can't sleep at night. Singing Rickroll from memory at 2am is possible.
But I don't like when it happens when I want to sleep because it annoyingly persists for a long time, even into my sleep.
In public settings I often make a deep "Hm-" mouth closed, I push it hard and short, I'm not sure if people notice it every time.
At other times when I'm in thought it's more of a "Hmmmm~" long and soft like I'm thinking, it's for vibrations and I also do it when I feel like singing in public.
Sometimes I start saying a sentence just because, no intention to actually say anything.