A certain young man was following him, wearing nothing but a linen cloth. They caught hold of him, but he left the linen cloth and ran off naked. -Mark 14:51-52That's it. That is all that is said about this incident. Mark's Gospel account is the only one that contains this story, and the young man is never mentioned again. Why is this story in here? Who is this young man? Why was he naked? These are all questions to which I have no answers. I do, however, have something to say about it.
In looking a bit further into this, I found something very interesting. The Greek word for "linen cloth" that is used in this passage is only used three times outside of this story in the New Testament, once in each of the first three (or synoptic) gospels. Any guesses on where it's used? If you guessed that it is used as the linen cloth in which Jesus' body is wrapped after the crucifixion, you are correct.
What does this mean? I don't know. Perhaps it's foreshadowing the resurrection and telling us that not even wrapping Jesus in a burial cloth (i.e., Jesus being dead) will prevent Jesus from being free. I'll let you come to your own conclusions on what this small portion of the Gospel means.