At some point, all effects require a cause. The "nothing" postulated before the "Big Bang" had to truly be nothing - no time, matter, energy, anything. If there was "something" (the singularity) before the Big Bang, what caused it to Bang? If it was something internal to itself, why did it bang when it did? What initiated the cause? - In the end, there must be a First Cause - a starting point for all causes.
It is not practically possible have an infinite series of events in the past and the Second Law of Thermodynamics prevents there being an infinite expansion-collapse-expansion of successive universes.
The best statement of the situation before the Big Bang is the Kalam Cosmological Argument :
1. Whatever begins to exist has a cause of its beginning.
2. The universe began to exist.
3. Therefore, the universe has a cause of its beginning.
If there is nothing before the Universe begins, what caused it? The only logical answer is something timeless (not dependent on time or outside of time, which did not exist), space-less (does not occupy space that did not yet exist), immaterial (not composed of matter, which also did not exist), powerful (able to provide all of the power necessary to generate the matter and energy in the universe - think E=MC2), and intelligent/willful (the fine tuning of the universe for life implies it is deliberate, only a mind or will can initiate a creative act. Forces respond to other causes, they cannot initiate anything - just as nothing can initiate the creation of something).
For a fuller explanation, I suggest a visit to
https://www.reasonablefaith.org/writings/popular-writings/existence-nature-of-god/the-kalam-cosmological-argument.
From Psalm 19:
1 The heavens declare the glory of God;
the skies proclaim the work of his hands.
2 Day after day they pour forth speech;
night after night they reveal knowledge.
3 They have no speech, they use no words;
no sound is heard from them.
4 Yet their voice[b] goes out into all the earth,
their words to the ends of the world.