Part of the reason I believe in God, in addition to the personal experiences I've had over the years, is the fact that God makes sense out of a lot of things. Here are some things.
God makes sense of existence
As JJAC said, you don't get something out of nothing. You can't get a universe out of nothingness. Cause and effect just don't work that way. If something comes into existence, something must have caused it. Whatever caused the universe must have been able to exist outside of space and time, not made of matter or energy, and unchanging. It must have been incredibly powerful and intelligent to make a universe that life can exist in. The best explanation is God.
God makes sense of the universe
Quite honestly our universe just should not exist. There are many constants in our universe (unchanging values) that if changed ever so slightly, the universe would either be inhospitable to life, or non-existent altogether.
Here is a table that shows what I mean. The odds are so incomprehensibly low that this is the result of pure chance that to suggest it "just happened" is worse than magic. The only two other possibilities are physical necessity (it "had to be this way") which remains unproven, or that it was designed by a mind. The best explanation is a mind, which we call God.
God makes sense of morals
Are there certain things that are right or wrong whether or not someone says so? If so then we must ask, where does that notion of "right and wrong" come from? Only a person can impose morals. This points to the existence of a God who has laid down morality for us.
God makes sense of Jesus
Jesus of Nazareth is not a made-up figure. Several ancient historians speak of him as a Jewish rabbi from Judea, considered God by his followers, who claimed to perform miracles. He later died on a cross and his tomb was eventually found empty. What's the best explanation of this? Many will say that the disciples stole the body. But this fails because every apostle ended up dying for this belief, whether by their own hands or as martyrs. And before then they spent decades under persecution and generally being disliked by many. Would you give up everything you have, endure hatred, then later die for what you knew to be a lie? Unlikely. The best explanation, in my opinion, is that Jesus was resurrected. And if this was the case, it points to a divine being, who Jesus called God, as the one who carried out the resurrection.
God makes sense of purpose and value
We all have an innate sense that we are valuable and have a purpose, and that those are present regardless of what others say. So if purpose and value don't come from other humans, where can it come from? It can only come from God.