When you take vitamin D it takes several days to build up in your system.  It's not like taking aspirin which is fast acting.  So don't see how there can be an association between vitamin D at bedtime and sleep. 

I am currently taking 10,000 IU of D3 and I always take it at bedtime.  If I don't take it then I sure don't see a difference in my sleep pattern. 

For several months last year I took 50,000 of D3 at bedtime and sure didn't sleep any better.  While taking the 50,000 IUs of D my creatine levels climbed over 2.3 and my doctor told me that that was a dangerous level and could damage my kidneys so I cut back to my current levels.  (Still don't understand how the body builders can get away with taking creatine supplements without damaging their kidneys.)  By the way, in the 1930s physicians were having patients take 200,000, 500,000 and even 1,000,000 IUs of D on a daily basis and were claiming the only side effects was artery clearing and disease prevention.