Where is your dog at night? In the house or outside? Maybe he is barking because he is frightened or feels he has to scare away unseen things in the night. I would suggest you have him sleep in the same room as you. Our dogs sleep on or near the bed. Once in awhile Hannah will get up and run to the front window to bark at some noise in the night. I bring her back and shut the bedroom door. She settles down with no problem.