Shaking head while talking?
Tics can come and go though...it's not a disorder unless it persists. I don't think it sounds like seizure activity but I'm no expert in that.
My son does weird stimmy stuff that is tic like at times (frequent throat clearly, vocal stims, etc. mostly).
I know that this is an old post, but I came upon it during a search for what my DS has been doing. This is exactly what I've noticed him doing this past week. When he is really concentrating on saying something his head kind of shakes involuntarily, like he is saying no. He also has been stuttering slightly. I haven't taken him to the doctor about this, but now I am really scared that he has ASD! Did you ever get any answers regarding this?