Hi, there is no rhyme nor reason for when it happens. For example - I had it on and off yesterday from about midday to around 5pm. Then it tapered off after my shower. Sometimes it happens until sleep time, sometimes it comes on in the morning.
It's not a pain, it's like a flutter, a twinge. If I put my finger down just under my clitoris, I can actually feel it twinge under my finger. It helps to sit down - the pressure against it lessens the twinging.
So weird! It's not all the time so I guess I should be grateful. My GP (who is wonderful), suggested the trapped nerve thing but she was unsure too.