I have a four-month-old puppy so aging isn't it. The rest of the family has been more responsible for his feeding schedule and checking his food bowl(Although they always seem to forget putting it away after an hour to train him to only eat during those hours) so I don't know about his feeding habits. I figured he was not getting enough play time so I went on a few half-hour walks with him, but he always returned to his behavior. During the walks he was just fine so I assume it has something to do with five people being in the hourse but all of them being busy at the moment with crap to take care of.
Four months is still very young, and while it is very easy to find people on the internet who will assure you that any and every misbehavior is a dire warning sign of a dog that will grow up and kill you in your sleep, in all likelihood it is just a phase and he will grow out of it. It is extremely stressful however.
Just do all the stuff you're supposed to do (exercise, lots of chewable toys for teething, bite inhibition, exposure to as many people and places as possible, crate training) and don't sweat the bumps along the way.
I'm only a first-time dog owner myself, but I can't list the number of problem puppy behaviors that just disappeared one day as my dog grew up. Nipping at our socks when we were trying to get dressed did not turn out to be an early sign of aggression, hiding under the couch in response to any sort of grooming did not mean he would never let us clean his ears, &c.