One reason why it took me so long to self-diagnose autism is that I thought I don't stim. In fact, once I learned that I do stim, my self-diagnosis process kicked in. That was the first time I said to myself that I might actually be autistic.
The reason for this misunderstanding was that I thought stimming is stereotypical, very repetitive, compulsory movement. I guess this misunderstanding is quite common.
I've since learned that stimming, short for self-stimulatory behavior, is basically stimulating one's sensory system in certain ways. It may be a way to soothe oneself, help to focus in overwhelming situations by feeding one's brain predictable sensory input, a way to express joy, or simply something that feels nice. Movements are part of it but any sense can be used.
When googling the term, there are mentions that also neurotypicals stim but that when diagnosing autism, stimming is somehow different -- only socially unacceptable stims are "real" stims. Bah.
I've started paying attention to how and when I stim, and collect a list of stims I do. I've noticed all types of stimming behavior (soothing, focusing, joy, fun). I do it more than before -- or maybe I just notice it more often. I've noticed that I love moving my body parts, especially to music. I also love different textures.