A negyedik munkás nem dolgozik, ő szédül.
is this construction natural? without any pronouns before szedul
I was wondering that too...
I think so, it's reasonably common in languages with consistent conjugation (like Spanish but NOT like English which is very inconsistent) to drop the pronoun, since it's made redundant by that same verb conjugation.
Yes - the use of a pronoun is the exception. It implies emphasis.