OK so I find this kind of weird. They don't do this a lot but sometimes when I'm holding one or both of my girls they vibrate. They don't really make much of a noise along with the vibrating the just do some light vibrating almost like purring but without the noise. Does this mean they are uncomfortable with me petting them or is normal and nothing to worry about? They do it after a bath but I feels a little more like shivering so of course I wrap them in towels and make sure to change them when they get wet until their dry so they stay nice and warm. Is it another way of saying they like being pet? It's not real often they do this just once in a while.