My husband says I do this to him all the time, though I'm still asleep myself when it happens. He'll try telling me to move over, knock it off, etc., but if I keep it up after a while he'll start playing back. Usually I immediately scoot over to the far side of the bed, but every now and then it's gotten to the point where I've woken up with him full-on going for it.
It seems weird to say, but whether it's due to the fact that my brain is still half asleep (and therefore confused) or some other reason, this has been some of our best sex!