Computer won’t boot into BIOS

I have an Ubuntu machine built by Lambda labs with 3 Gpus.

When I try SSHing into it, I can use the computer, but the system keeps killing processes that use the GPUs.

When I plug into a monitor, the computer boots up into Ubuntu, but then after about 30 seconds the GUI dies and goes back to login screen. This happens in a cycle.

Both of the above indicate to me (please correct me if I am wrong) there is something wrong with GPU drivers.

I decided to reinstall Ubuntu. I have a USB boot drive that I have verified works. However when I plug in the drive and try booting into the BIOS, the monitor just says no signal and I can’t see anything. I have tried all the available HDMI ports in the machine. I also have verified independently that the monitor works.

Does anyone have any idea how to solve this?