ichidan verb
begin to walk; set out
Used when someone starts walking, either literally or figuratively as the start of a journey or activity.
赤ちゃんが歩き始めた。
The baby started walking.
彼は駅に向かって歩き始めた。
He began walking toward the station.
Compound of 歩き (continuative form of 歩く 'to walk') + 始める 'to begin'.