Black screen from a Linux VirtualBox guest machine

As I'm using several very different environments for some projects I'm working on (embedded software, application server, Android, etc.), I set up one VirtualBox virtual machine for each of them. The guest machine OS is Linux, and I run them either on a Linux host, or on a macOS host.

Over past weeks, it happened several times that right after having restored the state of a guest, I get a black screen . I tried to enter the control sequence that usually displays a console, but never succeeded in getting it captured by the guest.

Today I decided to get prepared for the next occurence of this problem. I installed an SSH server (openssh-server) and looked for a way to get the IP address of the guest VM. This can be done thanks to the command:

VBoxManage guestproperty enumerate <guestName>

So, next time I get a black screen, instead of performing a hard reset of the guest, I'll try to connect into it, and investigate what's happening.