I don't drink a lot of coffee so I've been doing just fine with my hand grinder… except every time I use it this happens. I don't exactly know why 
@lumi does this, but as someone trying to learn more about canine behavior it utterly fascinates me.
Usually when she does the "humping" it's attention-seeking behavior (e.g. she wants me to play with her, or she wants to get the food I'm preparing). But that doesn't fully explain this, triggered by the sound of the grinder.
Fun fact: the same thing happens when I blow my nose. 
God I love this mysterious fluffy rascal... 