He who He
There’s no existence if there’s no beginning its just like an analogy of cause and effect. God claims that He is the beginning, so He is the first cause and the effect is the creation. He is self existence and self sustaining entity.
Answer
Its quite simply the nature of the human mind not understand the concept of everlasting being, and eternity etc. Consider the human life, it “starts” somewhere and “ends” somewhere. This has shaped human thinking form the very beginning. The human brain, which uses less than 10% and is regarded as “intelligent” cannot fully comprehend the concept of eternal being. We may be the most intelligent of creation, but that in itself tell’s you why we cannot understand, we are “created”, God “exists”.

 Islamic Answer
First I ask you, can you count (do you know how to count)?
I give an example of numbers.
If we take the number zero (0) as the middle.
under the zero (0), it goes from 0 to -1 to -2 to ENDLESS,
do you know the begin under the zero? (or you can say the last (negatif) number under the zero)
and from zero (0) to above it goes from number 1 to 2 to ENDLESS.

conclusion: numbers have NO BEGINNING and NO END, just like Allah swt.
[Quran 57:3] He is the First and the Last, the Evident and the Hidden: and He has full knowledge of all things.

yes and just like god/Allah numbers don’t exist they are a man made creation!

THE SCIENTIFIC ANSWER

Actually this common question always gets it backwards. It would make more sense to ask: “How can something exist that has a beginning?” Things which exist are made of matter. Things can change in form but can not come into or go out of existence – the matter remains. You can form bricks from mud, then houses from bricks, and in time the house will again return to mud, but the matter involved did not have any “beginning” and can have no “end.”

Anything and everything in the universe, whether a solar system, an electric toaster, or a Baptist Church is comprised of matter which was re-combined to form a toaster (or whatever) from always existing matter. If the Church burns down, the matter still exists (and fertilizes the soil).

When you freeze water into ice, the ice was not “created” from nothing – the matter just changed form. In the context of the matter of which things are made, nothing which exists had a beginning. The Universe is a sum total of all existants and all of the matter these existants are made of. The Universe did not have a “beginning,” but like water and ice, it changes forms and arrangements of matter over time.

But if Nature and Natural Law are too boring for you, by all means create a God and say he did it all.