Growling German Shepherd at night

Question
My 2 yo/non-neutered male German Shepherd is growling at me, and mainly my wife at night when we touch around his face. At first I thought it was an ear infection or a tooth problem but they both check out fine. We have a female/fixed 1 yo 40lb mutt that he does not act this way towards.  It is very strange behavior - one minute he's the life of the party and the next - skiddish and growling when you try to give him love. This only happens at night. It has never happened during the day. The other dog doesn't even notice but we are afraid he will do something to us, someone he knows, or a stranger in one of these episodes.  

Answer
I am sure this is a leadership problem.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

You should neuter him too.  Certainly any dog showing such aggression isn't a candidate for breeding.