It is completely understandable why someone might ask this question, but it unfortunately misunderstands the Christian argument. This question seems to imply that the Christian argument is “Everything that exists must have a cause.” However, the Christian argument is somewhat different: “Anything which has a beginning must have a cause.” Christians believe that the universe had a beginning, and therefore had a beginner (who we identity as God). Christians do not believe God had a beginning, so there is no need for God Himself to have had a beginner.
The Bible teaches that God is eternal, that He had no beginning and will have no end. This idea may appear foreign at first glance, but I would suggest that everyone, if they really think about it, likely believes something is eternal, even if that thing is not God. I’ve talked to people who do not believe that the universe had a beginning.
Ultimately, everyone points to something eternal that is the cause of all other things.
