Is it possible that the Universe is expanding due to additional Big Bang events?
You may need to revisit the theory behind the Big Bang. The Big Bang is more or less a description of what the early universe looks like if you view expansion in reverse. The single "Big Bang" at the beginning of our universe is the only "Big Bang" event predicted by expansion. Also, the Big Bang did not happen in a single place, it happened everywhere in the universe. Finally, the Big Bang did not create space-time, and the expansion of the universe is not the creation of new matter. The Big Bang describes a time when the metric of space-time was extremely dense, and expansion is the metric of space-time increasing as below:



The distance between points in space increases, but the same mass-energy is there as before.