Learn Russian: Я энергичный человек и люблю физическую работу, причём быстро восстанавливаюсь. - I am an energetic person and like physical work, moreover, I recover quickly.

Причём doesn't just link two equal facts; it adds an extra, emphasizing detail that builds on the first part. Here, the fact that you recover quickly amplifies why you like physical work or proves just how energetic you are. It translates well to 'and what is more' or 'moreover'.

Could I use притом instead of причём in this sentence?

Yes, they are often interchangeable when adding a supplementary fact. However, причём is much more common in modern conversational Russian for this kind of seamless addition, whereas притом can sometimes sound a bit more formal or bookish.

Why is there no я (I) after причём?

In Russian, when the subject is exactly the same as in the previous clause, you usually drop it to sound more natural. Because the verb восстанавливаюсь clearly ends in the first-person singular suffix -усь, it is completely obvious who is recovering.

Why is восстанавливаюсь in the imperfective aspect here?

The speaker is talking about a general trait or habitual action: they always or typically recover quickly from physical work. If they were talking about recovering from one specific grueling task in the future, they would use the perfective восстановлюсь.