But then I'd have to go turn it on when I actually need to use it...
So I automated it with doormouse - its a wake-on-lan reverse proxy, both or web apps (HTTP) and things like SSH (TCP).
When I connect to the services hosted on my old NAS, doormouse wakes up the machine and fulfills the requests when it has woken up.
It is open source, yes a lot of the code is AI-generated, but its heavy on the tests, both automated and manual.
Try it out - feedback is welcome.