I have caught myself doing this from time to time. Specifically, rocking, lining-up objects, and forcefully keeping all my steps the same length. I've done these things since as long as I can remember. I've caught myself doing these things much more often over the past two weeks.
Considering the Quirks thread, I am thinking this actually very common behaviour.
I was suspected to have Asperger's a little while back, but I think a lot of people may exhibit the same behaviour, and have "circumscribed interests" as well.
Anyway, do people know people who fit these characteristics but do not have a PDD of any kind?
I'm asking because I never got off of the mailing list for the local Asperger's meetup, and I got an invite the next meet-up.