Someone reported workshop content causing memory leaks, but that is probably unrelated as you’ve been having this issue since before the workshop update.
We could try a few things to solve it, but before I mention those, do you crash in any other video games? Also, what’s your hardware setup? Do you think you could possibly have an insufficient power supply, or a faulty one? (Also any other faulty hardware, like a graphics card or ram?)
Have you updated your graphics drivers recently? If not, try that. Solves a lot of issues in a lot of games.
If you have two monitors, open task manager on the one you’re not playing games on, and monitor it. (Resource monitor works a little better, but task manager will get the job done on the performance tab.) If you only have one monitor, you can use resource monitor, and when the game freezes when it’s about to crash, Alt+Tab to resource monitor and see if anything is pegged out (CPU, Hard drive, Ram). If you have Windows 10, task manager will also show you your GPU usage, but I believe resource monitor still wont.
You could also be having an overheating issue with some hardware component. Check out HWmonitor by CPUID. It will show you the temps of all your components.
Make sure Windows is up to date as well. I know Windows 10 is pretty forceful about updates, so you should be fine if you’re on Windows 10, but if you’re on Windows 7, double check that you’ve done updates recently.
Also, try verifying the integrity of the game files through Steam (how to: https://inxile.zendesk.com/hc/en-us/articles/115004662908-Verify-game-cache-files-Steam-)
Lastly, you can try reinstalling. A lot of times, when you have an issue with a game and nothing will solve it, uninstalling, restarting the computer, and reinstalling will fix it.