I thought odpoczywa means relaxing as well not just resting
I personally think it's a little bit of an overinterpretation, but Wiktionary thinks the same as you, so let's say it's close enough.
But as Mateusz said, there's a separate word for "relaxing".
Yes, it could be as well but odpoczywać literally means to rest. There's a verb relaksować się, but odpoczywać can be used for both
Why not correct: The young doctor is resting after his work.
Seems correct, added now.