ichidan verb, intransitive verb
start doing; begin to do; get going on
Compound of やる (to do) and 始める (to begin). Used when someone starts doing something, often with a sense of initiative or finally getting around to it. The intransitive label is unusual; in practice it often takes an object marked with を, functioning like a transitive verb.
そろそろ宿題をやり始めよう。
Let's start doing our homework soon.
彼は新しいプロジェクトをやり始めた。
He started on a new project.