I have one doberman, just turned about 1 year 4 months. very similar issue though. he is very loving and sweet all day to my husband and myself and anyone who comes in the door. but he was randomly wake up in the middle of the night and its almost as if he doesn't know who we are starts growling and nipping at us. never has drawn blood, but it's quite scary. he gets better once we turn the lights on and then typically runs out of the room and sleeps on the couch. we have a night light so the room isn't completely dark. it just started happening 2-3 months ago. and it's very random, not every night, but occurring more frequently. he has slept in our bed with us since we first got him at 2 months. I can't think if any change in his day-to-day patterns that would cause this abrupt change. any thoughts?
Due to the age, I would wonder if it's not a high dose of a fear period. Does he do this anytime he naps or only at night? If only at night it might be time to crate him at night. I'd also seek out a vet to make sure nothing neurological is going on.