Alan F. Segal wrote a book titled "Paul The Convert: The Apostolate and Apostasy of Saul the Pharisee" which solidly puts Paul into the context of a first century stream of Merkabah Mysticism. This was operational within the prophetic streams of Judaism - especially Ezekiel 1 which is likened to both Luke's and Paul's own description of Kavod or Glory coming from the light Paul encounters with all the images explored in the Oracle of the Phoenix, such as the Cherubim, throne, etc.
Beyond the 2nd chapter of Segal's book, I'm also attaching a review of its entirety by Cary C. Newman of Baylor University Press.