I have a little guy who was just like that, at first. Had not yet learned to put himself to sleep (we did let him cry it out) and then when he was asleep, would wake after 30-40 min but still be exhausted. I talked to mom, who says "oh, he's just not a sleeper". Seemed to me that he was just being picked up out of bed at the smallest squawk. So again, I just allowed him to calm himself, and sure enough he learned to put himself back to sleep.
Worked for us, hope it works for you.