I will be keeping an eye on this thread to see what other people do, but what I have done in the past is to have a couple different health checking strategies.
For web-accessible services I am running, I usually run something like Uptime Kuma or Gatus on a different box checking to make sure those web endpoints are available and performant. I lately have been really digging how Gatus can check more than just the response header, but also latency and certificate validity.
For the host machine, you can set up custom alerts within netdata for stuff like cpu utilization and memory with custom thresholds. The only other solution I have used for this in the past is setting up alerts through my VPS provider (if it is a VPS that is).
On really low-spec machines I have had trouble with netdata though, so I don’t have a good solution in those cases. Interested to see if there are less demanding options. Instead, I have resorted to just using dashdot as a PWA so that I can check it easily on my phone if I am on the go.
For some custom services in the past that run on set schedules, I have used healthchecks.io (which you can selfhost) to send alerts in the case that they don’t run for some reason.
As for the containers being restarted, I actually don’t have experience with that, so I am interested to see what others have done.