Hi thylacine,
Welcome to Psych Central.
My son is like that. He sleeps very deeply and I have had to wake him up in the morning and we carry on a conversation, I think he is awake and then come back later and he is sleeping (and often late to where he needs to be). He has no memory of the conversation or anything, even though he seemed to me to be wide awake. Sometimes he is grumpy, sometimes not. It can be frustrating to me, but I know he isn't doing it on purpose. To him, he just woke up and he doesn't know why I'm frustrated.

I'd definitely try to let your wife know that it's not something you are doing on purpose and if this is interfering with your well being (or your wife's ), it might be a good idea to go get checked out. Please let us know how you get on and again, welcome to Psych Central.