Help diagnosing really obscure computer freezing issue

I have a Gigabyte Mini PC I bought back in 2017. Initially I ran Ubuntu Desktop on it, and it ran fine for a couple of years. Then all of a sudden, it started randomly freezing, and I could only resolve it by rebooting the machine. The computer started to become kinda slow, and the issue persisted. I tried troubleshooting without any success or hints as to what might be the problem, so I eventually just abandoned it, put it in a closet, and got a new computer. Fast forward to today, I'm getting into home labbing, and I pulled out this "old" PC in hopes of repurposing it. I wiped it clean and installed Debian 12 on it. Ford the first few days, it ran flawlessly. I got excited thinking maybe it was some weird software issue, and that a fresh OS install might have helped. Then one day, I noticed upon waking it from sleep, it would often freeze on the user login screen... I'd have to put it to sleep and re-wake it, or straight up reboot it to get past the freeze. Now, it's escalated. I'll be using it, and suddenly a noticeable lag/slowness in performance will kick in. Then, the fan revs up and it will completely freeze on me. Only rebooting it helps. I am now starting to wonder if it's a hardware issue? My hope is that this Mini PC is still salvageable, and that I can use it as part of my home lab setup. Here are the hardware specs: - Intel Inside Core i7 - Iris Pro Graphics - 250 GB Samsung SATA SSD (6% used) As mentioned, I'm running Debian 12 on it. The mini PC model is GB-BXi7-5775 I'm at my ends reach trying to figure out what's wrong. ANY assistance with troubleshooting (what to look for, where to look for e.g. system logs, etc) would be immensely appreciated!