The answer is Yes, I had a boyfriend that I did this with multiple times… at least three occasions that I can remember. Having a penis in my mouth is very soothing, like a pacifier to a baby.
Here’s how it worked: he would lay on his side, and I would spoon around his knees with my head propped up by a pillow so that my face was even with his Cock. We would both be excited by it at the beginning so there was always an initial intense session resulting in an orgasm, and once that was out of the way we would drift off to sleep. He would lose his erection after that first orgasm, allowing me to snuggle up against him and just relax with his limp Cock filling my mouth. While I would gently suckle on him while drifting off, once I was asleep that stopped and my mouth would just hold his Cock while we slept.
REM sleep causes erections, so several times during the night I would be woken up by the Cock in my mouth growing too big for my mouth to contain. (Sadly I’ve never mastered being able to deep throat.) Let me tell you, there is no greater feeling than the initial moment of confusion of crossing over from a dream into reality and realizing your mouth is actually full of Cock. Upon waking up I would start sucking again, which would lead to him cumming again, and then we would both drift off to sleep again, neither one of us having said a word. And then the whole cycle would repeat again and again until morning.
Now the drawback to all this is that we were both having our REM cycle interrupted all night, and we would both be exhausted all the next day. As a result we didn’t do this all the time but saved it for a special treat. The memories of those nights and that feeling of waking up with my mouth full are some of the best sexual memories of my life.