Pokey oaky, back to the OP… Sniffs_Markers almost always wakes up a 4:30 a.m. with a horrible feeling of dread, and as you describe, once she convinces herself that all is well she nods off again, usually within five minutes and then is perfectly fine throughout the day.
Her way of coping with this bizarre “waking” --BTW – is to recite the prayer that goes “the Lord is my shepherd…” and she’s usually sound asleep before she gets to the bit about “green pastures”. It seems to comfort her enough that she no longer finds the strange waking bothersome.
We’ve no idea what causes this “dread rousing”. It’s almost always at the same time (around 4:30 a.m.), no matter when she went to bed. It also seems independent of her general mood at bedtime and the following day. It’s not sleep apnea, her breathing seems pretty regular to me.
Perhaps it is some kind of mild “night terrors” – provided that “vague anxiety and malaise” qualifies. We think it is stress-related somehow. She gets it more when she is preoccupied, even though her stress is often “positive stress” (e.g. preoccupied with the next days recording session.)
We’re trying to notice if the time changes as the days get longer – we think that perhaps the early light of dawn maybe triggering some kind of anticipation of the day to come.