Cycling that quickly can happen in some people. Occasionally that happens to me too, actually it just did! I switched two nights ago into hypomania and then this morning I woke up hypo and within half an hour my mood completely switched. No triggers, nothing and it was within a minute this change occurred. I then proceeded to go back to bed and slept in till 1pm haha. However it should be noted I'm titrating up on lamotrigine atm and I took a higher than usual dose of seroquel to get to sleep and I'm sure that contributed to the switch as I call it XD.

While I don't think it's official there is ultra-rapid cycling which is within days/weeks and then ultradian (hours/days). Here's a link about it here which you might find useful Rapid cycling and mixed states as "Waves"