I have a 2 1/2 yr old german shepherd. Well trained on and off leash, friendly, good with other dogs, never any problems at all with aggression. The house consists of myself, my wife & our 7 month old gsd pup, no problems. Last night my wife and I came home from dinner, let the dogs out and were getting ready for bed, usual routine. The 2 1/2 yes old was laying on his bed as usual and looked "sad", ears down, head down. My wife approached him as she would normally and he let out a deep growl and continued to act strange. Growling, ant the fur on his back up as if he was scared...even towards myself, never snapping or lunging at us. I have him commands like sit and lay down he listened but still growling. After a few minutes he was back to normal, kissing and licking our faces. Well today, all day he was fine... Acted his usual playful self. Until tonnight the dog was in our bedroom my wife walked by spoke to him because he looked sad bent down to pet him and he growled again... She got up slowly left the room and he followed growling... He again also growled at myself. He just is acting strange... He seems out of it... When she would call his name he would come but growled. This has never been a problem and first sign was last night. He almost seems like he falls into a mood and then snaps out of it?We plan to take him to the vet tomorrow but just wondering if anyone had any insight???? Sorry so long... Concerned.