While in a document and after typing a complete sentence, when I press enter
a bracket appears before the first word of the new sentence. Why?

What type of bracket do you get? Is it like this "[" or "{". Does the
bracket print? Does it appear in a different color than your text?

Do you have track changes turned on?

"Brackets magically appearing in my doc" wrote:

While in a document and after typing a complete sentence, when I press enter
a bracket appears before the first word of the new sentence. Why?

I suspect that this is the paragraph mark. To hide it, click Tools --
Options -- View and uncheck Paragraph marks under the Formatting marks
section. These are harmless, as they don't print. No, let me rephrase that,
they are very useful, because they show you where each paragraph ends, and
paragraphs are a fundamental unit in the structure of a Word doc.
--
Ted