What Causes Abnormal Hand Movements In An Infant?

I have an 8 month old granddaughter who by all observations is a normal, healthy, happy child. However, she has a peculiar way of moving her arms and hands. She holds her arms out straight from her body to each side and twists her hands / wrists, almost like she is gunning the engine if a motorcycle. She does it when she is smiling and laughing, as well as when she is fussy or crying. I hear a lot about the Autism Spectrum. Is there reason for concern, and what type of doctor should we suggest that her parents take her to?