I feel your pain. I had the same thing happen to me on Saturday and it ruined my whole weekened. It was actually Saturday's migraine that pushed me to go online to find other people like me.
Sometimes I have woken up with migraines, but not for a while. It would usually happen when my hormone levels changed and they decided to change during my sleep schedule. Maybe you could be experiencing a shift in your chemistry.

Migraines, especially cluster headaches, like to hit just when the stress is leaving. It's akin to an adrenaline crash.

It is believed that when stress is VERY high, your cortisol levels keep the pain under control some of the time. However, when things start to calm down, the pain hits (along with a drop in your cortisol levels.)

This is the reason why many college students get a migraine AFTER finals, why people can often get through a crisis, only to have a migraine when it crisis is over, etc.

This makes sense also, because Sunday is the most common day of the week to have a migraine.

These are often called "Let Down Migraines" because they wait until the stress is over to hit.

I think they are common in most migraine suffers.

Hope you are feeling better.

Mine a triggered by humid weather, when i know we are in for a thunder storm,Stress is another but i also used to suffer from weekend migraines, i would have the kids all week and when they went to their dad at the weekend my stress level would change and I would get one every time, my doctor told me about the change in stress levels, now i have a trigger point at the base of my scull as it joins the right side of my keck, when that get tense i get them as well, I get at least two a week and self administer a morphin jab take two diazepam and that usually does the trick.