Yes, I know EXACTLY what you are talking about. I haven't felt that way in awhile, but I know it could happen unexpectedly.
It seemed worse during the acute phase, and I would fight it off, or distract myself a bit. A close relative died the day I quit. Just happened that way. So I allowed myself to grieve as early and often as possible.
I am also worried about being really depressed late into PAWS, if there are any serious depressive episodes happening for little or no reason, I will be sure to go to my psych dr.
He actually recommended the acupuncture for the depressing mood swings.