Some surahs begin without a lengthy preamble resembling the formal heading of a letter or proclamation. Without a heading does not mean the surah has no name; it means that its opening moves directly into the matter being addressed.
The opening may report someone’s words, present a complaint, declare a decision, or deliver instruction. Its immediacy draws the audience into the concern that the discourse is about to address.
Instead of objecting to the lack of a conventional preface, one should identify the addressee, subject, and purpose of the first sentence. These supply the most useful clues to how the following passages belong together.