What Causes Vibration Like Twitch Inside Vagina Lip?

About 1week ago I started feeling this little twitch on the right inside of my vagina lip, it's up by the hairline. It almost feels like a little vibration and it happens about every 30seconds to 1minute. What could this be from? It does not hurt - it's just a little annoying. Also I have not had sex for about 1month.