I think you need to see more than that to have Aspergers. DS is 7 and he's just now getting to the point where he understands that he is boring other people and refrains from going on and on about his idiosyncratic interests. Just last spring his speech therapist said she would turn his back on him while DS was babbling on (once going so far as to "hide" under the table from him) and DS would't even notice. Now just 6 months later his current IEP team (new people) is shocked that he was like that. They said it's actually an advanced skill for a 7 year old to realize whether they are boring their audience and what is appropriate to talk about with certain people (for instance other 7 year olds aren't interested in talking about Pearl Harbor).
DS walks on his toes sometimes and used to flap his hands and even with that the neuropsych who tested him said it's not enough. You need to fill out ASD inventories/checklists, look at things like "theory of mind" (there is a test for this), etc. The neuropsych who saw DS said a lot of clinicians diagnose based on superficial characteristics, so make sure you get a good eval. There are a lot of things that can cause extreme behavior. DD has ADHD for instance and has a lot of ups and downs and off the wall behavior. If your DS isn't that interested in other kids (4 year olds still don't necessarily play WITH each other that well, it's more parallel play), doesn't understand or enjoy social games, is obsessive about things (like needing to flip lights on and off), doesn't show signs of empathy, is very rigid about needing things to be a certain way--those would be red flags. I remember around age 1 1/2 or 2 DS was so quirky that I thought he might as well have ASD written on his forehead, but he would do things like give his sippy cup to another child who was crying and I knew he was probably developing normally. A lot of the quirks have decreased dramatically over time.
