Tail wagging--what does it mean?

Hello! My new chinchilla has been settling in well in the past week she has been here. She comes out to play and run all over my legs when I'm cleaning her cage. One strange thing she does is sit on her food bowl, squat down, waggle her tail, then she'll leap forward. She looks like shes playing around, but if it is a sign that shes agitated, I don't want to cause her any stress or upset her. Anyone know what the tail wagging is all about?

Thanks!