Problem with the root server

After regular server backup and update the root server does not start anymore.
I'm trying to fix that.

Root server seems to work properly now again.
Even the recovery console was not able to connect to the root server.
Hard reboot of the root server over the server provider web site seems to work.
I took took quite long.
But after some time the server did start again.
I could not find anthing usefull in the log files.
It seems like if the server simply switched itself completely off.