This is my first post on SF. I just wanted to give my 2cents...
I have officially named it
" Sneak attack from behind" 
I know it sounds horrible but it's never actually in the hehind. Before I mention details, just so you know. My wife know's I do this on occasion. She says as long as I don't wake her up, It's fine.
I have been doing the sneak attack from behind for almost 5 years. I have been married for 9 years. I have always been a touchy feely guy with my wife. When we are trying to sleep, I always have my hand on a breast or pubic mound. After she falls asleep I love to play with her clitoris and put my fingers inside of her. She is a very hard sleeper. It takes allot to wake her up. I would say once a month, When she isn't in the mood and I am horny as hell. I will try and put it in. She is normally sleeping on her side. I spoon her every night so she is use to me being close to her. Well, all I have to do is try and move her legs out so her butt is sticking out, and I have easy access. First I put a little lube on my fingers and put them inside her so she won't wake up when I put my penis in. After I play with her clit and rub her breasts, I am ready!! I gently scoot up to her and insert my penis slowly. This is so hot to me I rarely last more then 5 min inside her. I take it slow and enjoy. There has been times where she wakes up and tells me to let her sleep. I just masturbate then. She never knows how often I do it, but every now and then, I will tell her the next day and she is surprised. not mad.... She know my sex drive is way more then hers. She struggles to keep up with me. She has always told me once a week is what she would prefer and I have always said 2 times a day. So we make sure we have sex at least every other day. We are both 33 years old. we have 2 young kids. We both work and we have a pretty good sex life. Anyone else ever try this or had it done to them?