How do you translate to Latin "my work started here"? It is for a plaque on a commemorative bench.
I would suggest:
Hic opus inii.
"Here I started work."
It is common in classical Latin to use inire for starting a job of some kind (e.g. imperium, magistratum inire). Opus is used for many kinds of work, including works of art. I don't think an explicit "my" is needed here, as the person is clear from the verb.
I like a succinct phrasing like this, and it seems not to suffer from any serious ambiguity either.
Succinctness is one way to go about it, but I instead would opt for formality.
IN HOC LOCO OPVS COEPI
"In this place/on this site I began my work."
The bonus of using coepi is that it recalls annuit coeptis of the Great Seal of the US, which, even if you're not in the US, will still make it broadly recognizable.