Let's take throwing rocks from a highway bridge. I would never want to do such a thing, so knowing that I would get punished for it doesn't curtail my autonomy. I don't feel "forced" by those laws to not do it, since my own volition comes first. I think about the example of the doctor the same way.
Autonomy doesn't just mean being able to do random things and not being subject to thermodynamics and gravity and everything, in the context of a human being's will to live, it simply has to do with being subject to the will of another human being, and the reasons for that.
As Hannah Arendt said in an interview:
> The whole of Kants morality boils down to the fact that every human has to consider if each of their actions could be general law. This means.. it's the the extreme opposite of obedience, so to speak! Everybody is lawgiver. No human has the right to obey according to Kant. [..] We obey in this sense, as long as we are children, because it is necessary. There obedience is a very important thing. But this should end at the latest at age fourteen or fifteen.
In that sense, I would also make a distinction between discipline and coercion. E.g. choosing (and keeping to reflect on and affirming) even the most rigid principles and living by them is not a reduction, but an expression of autonomy. If you are your own captor -- and you're aware of it, and it's a voluntary choice, rather than a rationalization like like with drug addiction or mental problems -- then you're not really a prisoner.
When I work on something I love, I sometimes work my ass off. I could never ever work this hard on command, outside of a slave camp with actual guns pointed at me. There is simply no way. But when I'm in "in the zone"? I love it, because there isn't just pressure, there is also grip that translate it into motion in a direction that fulfills me.
The same goes for helping people or doing chores that I agree need to be done. E.g. once I and people from an FB group helped clean the flat of a woman who was lethally scared of an upcoming landlord inspection.. and so ashamed of the state of her flat that she actually wasn't even there while we did it. I cleaned nicotine stains from surfaces with baking soda for two days and it felt good then, and still feels good thinking back on it. According to her best friend who had organized the thing she broke out in tears of joy when she saw the result. If I had to do it for money for someone who then complains about the result, it would have been degrading. Same work, different context, completely different result. Extend that to a lifespan and it's really no wonder.
I think people can't care deeply about things they don't have some kind of ownership of, and doing things we don't or can't care deeply about makes us sick. Which is good, because it also means doing things we care about makes us happy, so let's do that :D