The beloved lightweight distro
This is definitely not a n00b friendly distro [1], I recommend sticking with stock-Arch or stock-Debian, learn their ways of doing things, then come back with experience to start using a distro like Bedrock. Far too many variables for what could be wrong and their documentation doesn't look that great, either. Good luck!
I'd ask here: https://www.linuxquestions.org/questions/bedrock-linux-118/
Hangs, reboots or does it turn off? Depending on that it could be a plethora of things.
Do you get any error prompts? Any red alerts when restarting?
Did you check that the monitor works steadily on another system/OS?
Did you try another DE, even on a live usb?
Is the HDD/SSD healthy?
Are all the fans working? Is it the thermal protection?
Is the PSU healthy and or the power connection damaged?
Does your system have a centralized logging like journalctl or can you reach the single log files to check and add more information?
It could literally be anything, even aliens.
General computing advice that’s stood for decades: if your computer is intermittently crashing for no apparent reason, check your memory. Every time a stick of memory has failed me, I always ended up chasing software issues first (and wished I had started my troubleshooting with passing an overnight memtest+ first)
I would have saved myself lots of time if I followed my own advice! :)
Have to agree with the other replies: this could be any number of things. I’d start with the basics by making sure it’s not a hardware issue, then looking at software. Vostro is Dell’s budget business line, and my experiences with Vostro have been lackluster at best.
That’s not to say it’s purely a hardware issue. I’m a hardware guy so I tend to look at hardware first. Any number of software issues could also be causing your issue, including drivers, driver configuration, data corruption on your storage device, a setting or config from your distro or upstream provider, or even some random utility you installed.
Does it crash under other operating systems? Does it crash only after sitting idle for a certain time? Are you able to open another TTY and use the system from a prompt even though your screen is black?
Could be anything. Hard to guess from just system specs. You have a old computer, that's all it says.