Isn't he too young to be getting lazier?

I've noticed Jake is not as active anymore. I mean, he has wayy better coordination, he makes huge jumps that are soo graceful and beautiful, and he still runs like a maniac in times of play. But, he used to play and sleep and do nothing else up until a few weeks ago. There wasn't a waking moment that he would just sit and relax, stare at something, etc. Now, I find him many times on the table sitting staring into space ...Also watching birds from the windows. Generally if he is left alone, he plays a little by himself, then stops and starts to just stare into space and relax...If I am there trying to engage him to play though- he never misses out and immediately gets drawn in. He does a lot more damage when he plays now, too. I came downstairs today and found a bunch of stuff on the floor, some oranges scattered around that were on the table and random pieces of paper. Lol he is crazy...but isn't he too young to be slowing down like this? He is about to turn 5 months old this Sunday (although it's possible that he is already 5 months old because Sunday is an estimate, I know which week he was born but not which day)..

Well, not really, if you think about it... He's a teenager or pre-teen... and they can be pretty lazy!

Plus if there's nothing to do... At least he's not 'sorting' your laundry for you or something.

I had a kitten once that would get more subdued for a couple of weeks, and at the end of that time, he would grow like a weed. I asked my vet and his comment to me was: growing takes a lot of energy out of you. He's just going thru growth spurts.

If he gets more active again and grows like a weed, this might be your answer. If he doesn't pick up again, you might have a mellow cat, or you might have a sick cat. Keep a very close eye on him to see any health changes. They can't tell you if something is wrong.