Why is the Pokémon Refresh button shaking?

Whenever I go into the menu, the Pokémon Refresh button wobbles and shakes to the side, even though nothing really seems out of the ordinary when I start it up. What does the shaking mean?


The button starts shaking when you need to take care of your pokemon. Taking care of your pokemon means to: A. Give them affection B. Feed them C. Play with them