I had trouble sleeping when I started Paleo and was taking my D3 at night before bed. Was nervous and couldn't seem to settle down. No problems since I went to morning, I have them with my fish oil right after breakfast.
After hearing Robb's podcast I switched my Vit D to night along with my Mg. MUCH better sleep. It's like I just pass out and don't remember the night at all and I wake up refreshed. There is probably no single right answer for everyone; and, it's so simple to test for yourself, that you should just do a week both ways and see what works best for you.
I tried taking vitamin D the evening first, and I was pretty anxious and could not sleep even with only 2000 iu/day. I switched to morning in past 2 weeks and I have been sleeping like a baby ever since. I think my explanation for sleep disturbance is that the fillers in vitamin D supplements could be the culprit rather than the vitamin D itself. I have bumped my daily intake to 5000 this past week and it seems to be working.