Maybe sudo systemctl restart gdm? That’s not quite the same as it restarts gnome display manager.

When your computer freezes and you can’t get to a tty with Ctrl+alt+F4 then it likely encountered a kernel panic. A panic is not recoverable. In some senerios I’ve seen the amdgpu module run into a kernel oops which is recoverable. It doesn’t really effect the desktop other than a studder as the kernel reinitializes in the background.

If your system is freezing start by checking RAM and then try a different GPU. Its likely a hardware issue