Beginning to exist ex-nihilo (out of nothing) is a very human concept. An event "began" when we quantified the combination of states of affairs that match our concept of an "event" and then call it that. A carpenter doesn't bring a wooden table into existence out of nothing, they rearranged wood that existed, into a combination that we identify as a table. Nothing came into existence, it just began to take a shape that matches our concept of a table. We do not have any evidence to suggest that actual quantum particles come "into existence" (out of nothing).
Understanding this is important for not feeling the need to rely on a God concept to explain the universe and ourselves.
Recognizing that existence doesn't actually begin or end is very unintuitive for us because we constantly observe things beginning to match a concept (creation ex-materia) and then to stop matching a concept (ending ad-materia). We understand and conceptualize the external world in terms of compound objects, not particles, atoms, etc.