In Exodus the most often verses used to try to "prove" the trinity are the "angel of the LORD" speaking through the burning bush, the supposed name of God "I AM" from Exodus 3:14, and verse 33:11 where YHWH speaks to Moses face to face even though no one has seen God at any time.
Trinitarians will sometimes say that the angel of the LORD speaking to Moses is Jesus. However Stephen tells us in the scriptures that it is not Jesus.
Acts 7:30: And when forty years were expired, there appeared to him in the wilderness of mount Sina an angel of the Lord in a flame of fire in a bush.
Clearly Stephen was in error if the "angel of the LORD" was Jesus or else we have to start believing Jesus is an angel. However, we know Jesus isn't an angel based on Hebrews 1:5.
​
For more information on why the "angel of the LORD" was not Jesus, see Exodus 3:2.
One of the most used verses to try to prove the trinity is that Jesus says "I am" and that he is somehow claiming to be the great "I AM" YHWH.
The term Jesus uses is "ego eimi" (to say "I am") but the problem they have with that is that many people in the bible say "ego eimi"
John 9:9 Some said, "It is he"; others said, "No, but he is like him." [The blind man] said, "I AM." (ego eimi)
For more information on why Jesus was not invoking the name of "I AM" see Exodus 3:14.
The expression "face to face" was a Jewish way of saying that the God of Israel spoke to Moses personally as someone speaks to a friend. To speak "face to face" or "mouth to mouth" was a Jewish idiom for speaking to someone in person. It is beyond doubt that Moses did not see the face of God for we learn immediately hereafter that God would not allow Moses to see his face. For more information see Exodus 33:11.