The discussion of the Son of Man in Daniel and in the Book of Enoch sheds light on how Christ uses this title in the Gospels. In Daniel it might not be entirely clear whether the phrase refers to a people as a whole or to an individual. But in the Book of Enoch, it is clear that it refers to an individual who is the Messiah, and who has the role of coming to judge and to reward the good and punish the wicked.
In many places in the Gospels Christ speaks of the “Son of Man” in precisely this way. Thus for example in Matthew 13 he explains the parable of the weeds:
Then he left the crowds and went into the house. And his disciples approached him, saying, “Explain to us the parable of the weeds of the field.” He answered, “The one who sows the good seed is the Son of Man; the field is the world, and the good seed are the children of the kingdom; the weeds are the children of the evil one, and the enemy who sowed them is the devil; the harvest is the end of the age, and the reapers are angels. Just as the weeds are collected and burned up with fire, so will it be at the end of the age. The Son of Man will send his angels, and they will collect out of his kingdom all causes of sin and all evildoers, and they will throw them into the furnace of fire, where there will be weeping and gnashing of teeth. Then the righteous will shine like the sun in the kingdom of their Father. Let anyone with ears listen!
It is probably a mistake to understand “Son of Man” here as simply a roundabout way for Christ to refer to himself. Rather, the Son of Man, namely the one described in Daniel and Enoch, is the one appointed to carry out the judgement, and the parable of the weeds is about this judgement.
There are many other places in the Gospels which speak of the Son of Man in the same way, as for example at the end of Matthew 16, when Christ says, “For the Son of Man is to come with his angels in the glory of his Father, and then he will repay everyone for what has been done. Truly I tell you, there are some standing here who will not taste death before they see the Son of Man coming in his kingdom.” The listeners will understand this to refer to the coming of the one appointed for judgement; they may or may not infer that Christ is speaking of himself.
Something related to this can be seen earlier in chapter 16:
Now when Jesus came into the district of Caesarea Philippi, he asked his disciples, “Who do people say that the Son of Man is?” And they said, “Some say John the Baptist, but others Elijah, and still others Jeremiah or one of the prophets.” He said to them, “But who do you say that I am?” Simon Peter answered, “You are the Messiah, the Son of the living God.” And Jesus answered him, “Blessed are you, Simon son of Jonah! For flesh and blood has not revealed this to you, but my Father in heaven. And I tell you, you are Peter, and on this rock I will build my church, and the gates of Hades will not prevail against it. I will give you the keys of the kingdom of heaven, and whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.” Then he sternly ordered the disciples not to tell anyone that he was the Messiah.
Mark and Luke have “say that I am” in place of “say that the Son of Man is.” Presuming that they speak of the same episode, as it appears, Jesus could not have literally used both of these phrases. Either he said “Son of Man”, and the other Evangelists, recognizing that Christ is the Son of Man, choose the shorter phrase, or he said “I”, and Matthew replaces this with “Son of Man.”
I cannot prove this, and nothing in particular rests on it, but I would suggest that Matthew’s text is probably historically accurate here. While Mark 6 does suggest that some people identified Jesus in such a way, “The Son of Man, namely the one coming to judge, is Elijah,” seems a more plausible opinion for people to hold than “Jesus of Nazareth is Elijah.”
Christ seems to speak of the “Son of Man” in general in the third person, but also apparently with the implication that he himself is the Son of Man, and this practice is likely responsible for the fact that the Evangelists in this case take the two to be equivalent.
One problem of course is that in the text at the end of Matthew 16, Jesus seems to say something false about the time of the judgement. Something similar seems implied by Matthew 10:23, “When they persecute you in one town, flee to the next; for truly I tell you, you will not have gone through all the towns of Israel before the Son of Man comes.”