When I get like that it usually has a lot to do with my anxiety level. Sometimes I'm just to tightly wound to stop moving and sometimes I just reach my threshold and can't do anything.

What I know about adult ADHD because my mother and best friend have it, is that they have a different internal clock, they lose track of time or think they can get way more things done in an hour than are possible. They can "hyper focus" on something really engaging. If they are highly stimulated they can focus on one thing for hours, to them it seems like twenty minutes.