Epistle to the Hebrews
Of all the Pauline Epistles the style in which the Epistle to the Hebrews is written is different from the others, why do you think it was done in this manner?
Most logical reason it sounds different is because Paul didn't write it. The idea that Paul wrote it came late and only out of the need to name an author. The first mention of the book or its author is by Origin (c. 185-254) who wrote "in truth God [alone] knows." Which implicates that they didn't really know who wrote it. In fact, it is anonymous, and it sounds different than Paul, talks about things Paul never spoke about, and likely was written after he died.