I've seen a few similar threads with people having reboots but my issue seems to be slightly different and was looking for any ideas/suggestions.
 
Received my 3080 on Friday and played on it for the afternoon with no issues though it did run "hot" (~83-84 C) on RDR2 1440p Ultra settings. Did some streaming in the early evening also with no issues. Began playing a game (Unfortunate Spacemen) with friends on 1440p highest settings and had the computer completely shut down with the inability to turn it on immediately after. Since it wouldn't immediately turn back on my first thought was the GPU or CPU overheated. Lights on the mobo were still lit while I was unable to turn on the PC. I had one additional crash that night while playing another game with a similar story however, I was monitoring using HWMonitor and Precision X1 and temps didn't look super elevated and may have been even lower than what I had on RDR2. Yesterday, I was playing SCP and had the same issue happen with GPU temps around low-mid 60s and CPU temps slightly above that. Previous GPU which is now back in the computer for the time being is an EVGA XC 2070 super which did not have any of these issues. Ambient room temp is usually in the low 70s F when it crashes.
 
PC Specs:
- Thermaltake V200 case 
- ASUS prime x470 pro motherboard
- AMD 2700x CPU (stock settings)
- EVGA FTW3 Ultra 3080
- Corsair vengeance pro 16gb (2x8) 3200mhz CL16
- Thermaltake Toughpower Grand 850w
 
Things I've tried after the first crash (most were done Saturday morning with 2 or 3 crashes happening that day total)
- Adjusted fan curve in Precision X1 to "aggressive"
- DOCP on and off
- Utilizing power target slider in Precision X1 to try 90% then 85%
- Adjusting CPU fan curve to "turbo"
- Updating BIOS on GPU based on this thread: 
- Moving slider to "OC" on card and trying the OC BIOS in the above link
- Adjusting case fan curves in ASUS BIOS
 
I may have forgotten some things that I've tried as I'm going off of my memory right now. Any help would be appreciated as I'd prefer not to RMA the card if there's a way around it. I've attached a picture of my build so you're able to see general airflow and setup.
 
Thanks!

What are the GPU temps with the case panel off?

- Thermaltake Toughpower Grand 850w - this might be one of the PSUs that cannot handle the 30 series transient power spikes that cause a PSU to go into shutdown (yes, reports of some 850+ watt power supplies not coping and shutting down have been reported).
 
Test with another PSU, test in a friends computer, search for info on the 30 series and this PSU.

I had not tried with the panel off. I'm guessing that would test out if airflow through the case is adequate based on the differences in temperature? I can reinstall the card and try that later today.

If this were the problem, would there be a solution possible with the current case (e.g. adding fans) or would the best solution be a case with better airflow?

ToeKneeAy
I had not tried with the panel off. I'm guessing that would test out if airflow through the case is adequate based on the differences in temperature? I can reinstall the card and try that later today.

If this were the problem, would there be a solution possible with the current case (e.g. adding fans) or would the best solution be a case with better airflow?

 
Lets see what you get 1st. :)

Thanks for the reply. I have a 2nd PC but unfortunately the power supply in it I think is around 500-600 watts and doesn't have enough PCI-E connections. No access to other computers.

When playing RDR2 and having the temps up to the 80s I was also watching the power consumption on HWMonitor and it maxed out at 103% (before I adjusted it down). Would you think trialing moving the power target to 80% or so would be an adequate test for this? I just checked local stock of power supplies and there's no store around that has stock of PSUs within the recommended range so I will look to see if there's any additional info I could find.

Transient response of the power supply is probably very poor,  I'd suggest a better unit.

I thought a little bit more about the power supply and wanted to also clarify another point: when the computer shuts down trying to power it on immediately does nothing. It takes around 5 minutes for the power button to become responsive again and turn the computer back on.

This led me away from the PSU being the culprit and thinking it was more a thermal issue as if it were just the PSU load, I would assume it would reset the computer but allow it to turn on again immediately once the load it couldn't handle was resolved.

Let me know if this thinking is flawed in any way. Unfortunately, if it's the PSU I won't be able to get my hands on one to test for a little while.

83-84c isn't hot enough for it to shut the PC down.  I'd try to find a better power supply.

ToeKneeAy
I thought a little bit more about the power supply and wanted to also clarify another point: when the computer shuts down trying to power it on immediately does nothing. It takes around 5 minutes for the power button to become responsive again and turn the computer back on.

This led me away from the PSU being the culprit and thinking it was more a thermal issue as if it were just the PSU load, I would assume it would reset the computer but allow it to turn on again immediately once the load it couldn't handle was resolved.

Let me know if this thinking is flawed in any way. Unfortunately, if it's the PSU I won't be able to get my hands on one to test for a little while.

Sounds like OCP is kicking in on the PSU and it takes a little while to reset. I'd get another PSU.