Why is my vagina hole pulsating??

It's so weird I'll just be laying down or just sitting doing nothing and my vaginal hole will start quivering and like pulsating for no reason. I'm not making it do that, it happens on it's own and it just started happening recently. It's not painful or anything just kind of annoying and it's been happening everyday for weeks now. I'm not turned on when it happens either so I dont think its because of me being turned on or "excited."