Does anyone have any idea what could be going on when one's ability to perform Kegels fluctuates from time to time?

I mean, I have built up a fair degree of kegel's strength I think, but everynow and then, it's as though as nerve supply to that region is shut down or something, or blood flow is diminished, and I don't have much kegelling strength at all, and can only really kegel adequately standing up (not sitting down) and really focusing. Couple days later and I'm fine again. I don't think it's a muscle fatigue thing, it just seems to happen out of nowhere.

Anyone experience anything similar or have any insight as to what's going on?