My diagnosis is pretty new. I was officially Dx'ed in September 2015 (and unofficially in August 2015).

I don't have any agitation before my episodes -- at least not that I've noticed. Usually a change in my sleeping pattern marks the beginning of any episode, whether it's hypo/mania, mixed, or depression. That's all I can tell right now. But of course everyone has different hypo/manic symptoms, different triggers, and different "clues" that they're about to have an episode. So it's totally possible that agitation and impatience mark the beginning of an episode for you. Maybe you're experiencing dysphoric mania? I'm not sure. That's just my guess.