Wow, Brandi - I have the EXACT same thing. Exactly.

I've always slept on my sides and until recently, I never had any arm numbness (unless, very rarely, I fell asleep ON the arm and woke up with it completely dead...but that was different). Now, it happens in both arms and more often than not, it's the arm that's on top that goes numb. It's not like blood is cut off either...because with movement, sensation returns almost immediately, not after a minute or two of feeling the blood rush back in.

I've been attributing it to shoulder issues, because that's where the numbness starts (and extends down my whole arm and includes my whole hand). I also never had this until I started riding, so I figured it had something to do with the way the small muscles and tendons in my shoulders are changing due to cycling for my cardio instead of doing other activities. I figure that since I've bascially stopped upper body weight training (bad, I know) that once I get back in shape again, it might resolve itself.

I have also never felt any issues during the day. Weird!