I believe God exists simply by looking at the marvels of the things in the universe. We use the word cosmos to refer the universe because this word means orderly universe. The universe is indeed orderly!
No one would believe that a watch would fall into place all by itself; yet many people choose to believe that the universe, which is far more intricate, came about by chance.
The Bible also appeals to God’s creation as proof of His existence.
(Rom 1:20 NIV) For since the creation of the world God’s invisible qualities–his eternal power and divine nature–have been clearly seen, being understood from what has been made, so that men are without excuse.