For me, 90 percent of the spontaneous orgasms occur when the sex was especially good the night before and I sort of randomly "flashback" unintentionally the next day and I get to have that great feeling all over again. I tell my H that I'm thinking about the great sex we had yesterday (for some reason I have never told him that I am not just mentally reliving it-- and every once in a while it gives me a "jolt" that is a bit to powerful to enjoy, they'll feel "out of control"---it's totally weird and once again, I feel like I am a bit "crazy"). But if it happens because I'm thinking about someone else, I feel guilty and like I need to hide it from him!! So sometimes it is totally cool, other times not.