Why is my dog lazy? loves to lie down, sleep and look droopy even though he's well pampered?

since his birth, my dog, Bolt, has been like that. even when we give him food he still prefers to eat it while lying down on his side. looks like he's a very lazy dog! he walks slow, he always looks down and even when he comes to me to have is stomach scratched he walks to me in slowmo. but there are times during the day, usually at around 3 or 4pm, when he's really active. he jumps and runs around the house! haha!