does the time of running your intervals affect your sleep - is earlier in the day better for sleep at night?
I don't know, I've only done it later in the day. It takes a few days to sleep properly after a hard session though so although I expect it would help I don't think it would solve it.
At the point were I don't mind waking up at 4 as long as I can get back to sleep and if it's later I'll just get up and have a nap later. Anything worse is getting annoying.