Dancing without music

I like to dance in front of the mirror alone. No one sees me dancing. I don’t put any music and just dance alone in front of the mirror to the music or song in my brain. Is it haram to do that? I know that dancing in front of non mahrams is haraam and if danced in front of mahrams, then there should be no any vulgar moves. But my question is that is it permissible to dance alone in front of the mirror with no music or songs but with a song inside my head or I’m singing it. That is my question.