Question CPU fans occasionally burst to 100% and crash my system.

[tete56]

A week or two ago my system (assembled in September 2018) started having these weird crashes. This is all predated by me blowing through my pc case with canned air like I do once in a while.
My system specs are as follows

Windows 10 professional

nvidia geforce rtx 2070 GPU

intel i5-8400 @2.8GHz

gigabyte b360m MBO

Kingston HyperX 2666 8gb RAM x2

Samsung 860EVO SSD as a system drive

Western Digital 1tb secondary drive

Seagate 1tb secondary drive

predator g-sync 1440p monitor additional hp x2301 1080p monitor as a secondary monitor

An older coolermaster B500 bronze PSU with no previous problems.

The CPU is (I would assume) more stressed than it should be during more mundane tasks but a 45 minute stress test using prime95 did not indicate any serious problems. But the crashes occur whether any major software is running or not. Once it has happened just after start-up after I returned home.

Sometimes there is obvious bottlenecking in video games like HITMAN 2 wouldn't run properly because my CPU wouldn't handle 1440p Ultra like my GPU would have liked. Could this just be a quality compatibility issue?

What could be the cause and what should I look to do to repair it?

 

[tete56]

I should also add that the temperatures were not unmanageable during testing, or have they popped out above 60 celsius in day-to-day usage. I haven't been able to get this data when a crash occurs.