Recently after the last updates I installed, I have been facing a strange issue if I keep the system idle for a few mins it froze completely for some reason, and I have to power off manually the system to fix it. I have no clue what caused the issue!
I recently read many posts complaining the same issue, and usually the reasons are the same, gjs and grep processes and browsers crash handlers running in background eating up all memory, consequently causing crashes, lags, and freezes. To prove it, beyond Storm suggestion (checking Logs is really helpful, I know) you can also monitor your memory usage in real time using System Monitor. It's better to know which ones are running so we can give suggestions and solutions accurately.
Hehehe, interesting, this is a browser I was going to start testing to see if performance improves (certain 3D games are really slow on the preinstalled Firefox), not yet started and soon read that has this problem . By the way, so far I didn't spot any issue about crash handlers on my Firefox, at least this .