I don't get any kind of "feeling" before or when I do the things I do that are considered stimming (picking / scratching at body, leg boucing, hand-wringing, drawing the same shapes in the air over and over with my foot / toes, and making patterns on surfaces with small objects at my disposal... this is an abbreviated list, too...
).
I pretty much do one or another constantly, but gently... or with the objects, small specks that no one tends to notice. But... I find when I am nervous or anxious, they can get a little out of control and other people begin to notice.
If they laugh and tease me in a friendly way, it helps. I can laugh at myself now. Not so when I was a kid. But if they make me feel weird about it, it just gets worse and worse!! !