Hi Greg.
That's very interesting. I'm the same way, it's hours 5-8 which seem to be the problem. If I sleep soundly during those hours, I wake up feeling like a truck ran over me. Also, I've noticed that I get very cold during hours 5-8, so I need lots of extra blankets.
I have at least 2 different sleep patterns. If I've had to deal with too many things during the day and didn't get enuf time to take needed rest breaks, my sleep will be short (1.5 hrs.) and sometimes deep, after which I awaken. Sometimes that gives me a total of about 4 to 6 hrs sleep per night. Some but not all awakenings correlate with bad pain breakthroughs, bad dream breakthroughs, or nothing I notice.
Nights that either follow days that have been pleasant, especially if I can get outdoors, allow for more restful sleep, often with 4 hr sleep periods rather than 1.5.
But, yes, times when for a few noticeable but different reasons I sleep very deeply and for longer periods than 4 hrs I will often feel worse next day. This is I think an important clue to one of the pathological mechanisms of ME. I've only come up with one explanation though it's grounded in no theory or research I know of. I often suspect that the reason for feeling worse after a deeper less broken up sleep might have to do with muscle tension or contraction; i.e., that the breaks on the episodic sleep nights gives you a chance to break into what might be tensing, contracting muscles and also maybe at a psychological level some safety from the control that comes from awareness of your surroundings almost to check that you're safe, which awareness is prevented by a long somnolent night. Why this would be I don't know but it does fit the hypervigilant states I believe have been mentioned as one of the many pathological symptoms that I think has been observed in us, certainly me.
Redclaylady