start (life) as (something)
Of a project or product, to begin from some particular, and usually markedly different, status, condition, type, etc. My first novel originally started life as short story, but over the years I just kept adding characters and plot details to it. The soft drink originally started life as a medicine used to treat headaches and anxiety.
start as something
to begin in some original condition or status. Every forest fire starts as a small spark. The argument started as a small disagreement.