I'm a warm-blooded guy, and I've always found that I sleep warmer (and better) when I only have shorts on. I'm always a bit cold when I get in the bag, but I warm it up fast.

In the morning, I will put some light clothes into my bag before I wake up so they warm up a bit. Then I put them on while still in the bag. This keeps me from getting out of the bag directly into the cold in only shorts.

I just got a new bag (Big Agnes) so I'm curious about how it works.

I think somebody hit it on the head earlier. Do what works for you.