Don Johnson

In my understanding, there MAY be some contexts where short hair would be a sin for a woman; this would be where short hair is a coded symbol for wantonness in a culture. In Corinth, some of the Greek temple prostitutes cut their hair to indicate that they would do anything and some of the high status Roman women also did this as a kind of hooker chic. This is obviously inappropriate for a Christian. But notice it is all involved in the motivation for doing it.

But there are lots of other reasons to have short hair that do not involve things like the above. As you mentioned, the Nazirite vows, where the hair indicated the time one was under the vow; it was cut at the start of the vow and at the end, the hair was then offered to God. If the person had to violate the vow, they then needed to restart the process, this is apparently what happened to Paul.