Did you suffer from hypogonadism or why you ended up using in the first place? Did you experiment with steroids and didn't do proper pct? Usually you are stuck with trt for life.
It's still impossible to say how long it possibly takes if somehow a restart would occur.
To put it this way, you won't make gains in the gym, you start to carry more fat and can't fight it off really, your libido will be non existent and most likely erection as well not to mention the negative psychological effects.
You might want to try restart with clomid perhaps hcg.
As such, no person or doctor in the world can answer your question. It'll be trial and error bro.
I wish you good luck, it's noble cause and IF you can restart to sensible T levels, consider yourself super lucky.
P.S: IF doc stopped you from getting TRT cold turkey just based on your levels. he's hideous.