It was an angel, it says so at the beginning of the passage in Exodus 3:
“And the angel of the Lord appeared to him in a flame of fire out of the midst of a bush. He looked, and behold, the bush was burning, yet it was not consumed. .” (Exodus 3:2)
This confuses some people when it says “God said” but it was an angel, but remember that the Hebrew word malak and the Greek word aggelos both just mean “messenger”. There are several passages in the Bible where the angel projects God’s words in the first person as “I”, rather than speaking of God in the third person “he” as does Gabriel, for example, in Luke 2 to Mary.