Why is my puppy jumpy and breathing fast? Is it normal or serious?

Thanks for using Petco Pet Education Center, formerly Petcoach. I can understand your concerns with having a new puppy. It is likely that your new puppy is finally starting to come into his own. As your puppy grows and matures he will start to develop his personality. This can lead to higher activity levels and more playfullness. As long as he is still tail wagging, running, jumping and overall seems happy, he is likely just fine. After quick spurts of play, puppies can also have heavy breathing episodes, but it should only last for 1-5 minutes at the most. If your puppy seems like he is in respiratory distress, coughing, gasping for air, etc, then its best to have him evaluated by your vet. At that point I would suspect he may have an airway infection, underlying heart disease, or a laryngeal disorder.
However, if your pupy is still playful, eating, drinking and normal acting, then he is likely just fine and is having over exerting moments of play. Just try to limit his play to no more than 20-30 minute intervals two times a day to keep him healthy. I hope this helps and best wishes with your new puppy Winter. Take care.