It's always either redundant or indicative of a problem elsewhere. Either section 1 has a title/thesis that makes it obvious what it's about and so the restatement is unnecessary, or you need to say it because you haven't already made it obvious. Instead of saying "This is the aim of section 1", just make the point of the section apparent.

This is a class of stylistic issue that's common in professional writing by those new to it and usually stems from a lack of confidence in the topic or in one's self.