20.04 server on raspberry pi 3 b+ when idle for more than 5 minutes

I have a fresh install of Ubuntu server 20.04 LTS for the Raspberry Pi 3 B+. I have not installed anything on it but I have run sudo apt-get update and upgrade. I have it in a "dead head" so I just use Putty to remote in. I have not installed a desktop just using the command line to force my self to learn Linux commands.

While researching how to run Boinc rosetta@home (the reason I installed Ubuntu server on the Pi) through the command line I noticed that the Pi freezes and hard reboot is necessary to reconnect. It will consistently do this.

Google has failed me so I am reaching out to the community. I have little to no experience, this was meant to be a learning tool I guess it is but beyond my ability to troubleshoot. Thanks in advance.