A console in an unknown state can often be recovered by entering Enter a couple times then
reset and Enter again. Even if it is not echoed to the screen.
Not enough information to determine what made it unresponsive.
Start health check monitors attempting to access this host over the network. Do this from several different points on your network and/or the Internet, to see what paths to it work.
Review logs for sshd or other services crashing. As this is systemd on Linux, use
Gather performance data over time, as comprehensive as you can. For example, consider netdata. Look for symptoms of very poor performance, like extremely high load averages, or paging out of memory.