Of all the names and titles that Jesus has, his preferred self-designated title is Son of Man. He uses it over 80 times in the gospels, far more than any other title. I've always thought that it was a strange title until I read up on it and learnt more about what it means.
The phrase the "son of man" is used two ways in the Old Testament. In places like Psalm 8:4 and Ezekiel 2:1, the phrase distinguishes mere humans from God. However in Daniel 7:13–14, the "son of man" reference is different.
Daniel 7:13–14
"I saw in the night visions,
behold, with the clouds of heaven
there came one like a son of man,
and he came to the Ancient of Days
and was presented before him.
And to him was given dominion
and glory and a kingdom,
that all peoples, nations, and languages
should serve him;
his dominion is an everlasting dominion,
which shall not pass away,
and his kingdom one
that shall not be destroyed."
This son of man seems to be greater than any human. The fact that he comes on the clouds is a clear symbol of his divinity (see Psalm 104:3, Isaiah 19:1). This son of man is given dominion and glory and a kingdom that will last forever! Clearly, this son of man shares qualities that only God has and therefore is God. This is the title that Jesus uses on himself. Jesus is claiming that the role of the son of man is his to fulfill. And this was exactly what he said to Caiaphas the high priest when he was on trial.