It comes on around the same time every day about 12:00 lunch time, then it waxed and wanes over the day, I think I expect it to happen at that time so it seems to start at the same time, for me being tired seems to help a little I think? I’m unsure. It does come on after an activity where I’m stimulated in some way, a conversation, a movie etc as soon as I go to change to another activity I seem to notice it. It’s so weird.