Fist-pumping baby or self-soother?!

Recently, Baby Linna has introduced us to her new bed-time/nap-time ritual. But we're not sure if she's fist-pumping, or if this is a self-soothing technique. We first caught her doing her "hitting" on her video monitor, but now she does it right in front of our faces! Maybe she's telling us she wants to go to the Jersey Shore this summer:) Does your child do this? What's the deal?