We often think of beginnings. How did something start? This is true whether we’re talking about human movements, epidemics (patient zero), or cosmology (Big Bang). God has something to say about His son Jesus:
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. – John 1:1-2, ESV
If you believe the Bible is the true, inerrant Word of God, then there is no question that Jesus has always existed. He has been here from the beginning.
The word choice John uses is interesting, because it also reveals something about the nature of Jesus. Jesus is God. But He is also with God, indicating some sort of distinctness from God. In Greek, Word is logos and God is theos. This word choice, as well as other passages in Scripture, is where we get the concept of the Trinity: one God yet revealed in three persons (Father, Son, and Holy Spirit). You’re not going to find the word “trinity” in the Bible. But it best captures what we understand about how God has revealed about Himself.
It is also important to note that in addition to being told that the Word (Jesus) was present from the beginning, that God was there then, too. “Beginning” is actually a bit of a misnomer, though. Beginning is based on our concept of time. It is better to say “has always been.” Jesus, the Word, and God have always been.
How did it start? Everything started with God, with Jesus, who has always been. Therefore, it is only logical that John starts with Him.