Generally, when I wake at 3:30 and cannot go back to sleep, I have a good idea of what's bothering me.
Often, I even know what I can do to address it (for example, if I am stressed about work, it is best just to work if I haven't fallen back asleep by 4 AM).
This morning, however, I'm just in a general state of malaise -- I'm frustrated with a few things but if you had asked me before I went to bed if I was particularly stressed, I would have said no.
And yet, I laid in bed awake from 3:30 'til 5:15 and finally got up to try to distract myself into a state where I can fall back asleep.
Maybe I'll do a little work, but only 'cause I can't sleep -- not because I won't get it all done if I don't do it now. I don't mind the early hours when I have to put them in, but when I don't have to...man, this sucks.
I do hope my subconscious finishes processing whatever is bothering it and lets me get back to a regularly scheduled sleeping program. Wish me luck.