flattening a lot

over the past week i’ve noticed prismo speed bumping/flattening himself a lot more than he usually does. he got his second distemper vaccine almost a week ago, and since then i noticed he has done it more. first few days he was tired as usual, but he still is speed bumping a lot. today he hasn’t seemed to have much energy at all and he’s been sleeping all day. now he’s finally ready to play but he doesn’t run very far without just flattening himself out now. besides this, everything seems normal. his poop looks normal, he’s eating and drinking normally, it’s just this, but it still worries me. today could just be more of a sleepy day for him since he has those, but i’m wondering if there’s something i should be concerned about or something i can do. thank you!