I've never temp'd myself, but as far as I can gather they recommend first thing on a morning as thats when 'most people' have been at rest for the longest period. I believe it can be done after a minimum of 3hrs sleep, so anytime of the day - just as long as its a min of 3hours sleep.
Not sure about the disturbed sleep though - are you unsettled all night long? As I have known people set alarms to wake them middle of the night to temp
Also, I think its recommended that you start temping from the 1st cycle day, so you can figure out your own natural temp before ovulation etc.
Good luck hun, let us know how you get on. x x x