Modern.ie Windows keep shutting down in VirtualBox
The virtual machine shuts down because it is not a fully licensed version. 30 days after running the VM for the first time, they will expire, and subsequently shut down after an hour.
You have to reinstall the VM.
To prevent that, create a snapshot of the machine after setting it up, and rewind to that snapshot once the evaluation period expires.
You can try open the command prompt and type:
slmgr /rearm
Ref: VirtualBox Machine auto shutting down, how do I stop it from auto shutdown