My little girl does this too. She does it after she pees or poops sometimes but she also does is when she wants something- like a toy that her brother has, a treat, or her dinner a little faster than Mommy is fixing it. It's almost like she's having a little temper tantrum. She will kick back and stomp her feet and whine or bark a little. It's so cute that it usually gets her what she wants so I'm sure that's why she keeps doing it.
