As you had already mentioned, it seems like the power supply could most likely be the culprit in my opinion. Under heavy load, the RX 7600 can draw as high as 200 watts, the r5 5600 can draw about 130 watts, and then you have to factor in any potential SSDs, HDDs, CPU Coolers, Fans, etc and any associated spikes in power draw. Depending on the age of the power supply, it may have lost some of it's initial wattage capacity and brought you closer to the edge of it's limits.
A few things to try:
- Monitor your CPU and GPU temperatures and make sure they are not going above 85C
- Uninstall your graphics drivers using the Display Driver Uninstaller from Guru3D, then reinstall them using the latest AMD Adrenaline software https://www.amd.com/en/support/downloads/drivers.html/graphics/radeon-rx/radeon-rx-7000-series/amd-r...
- In the AMD Adrenaline software, try going into your GPUs performance tab and temporarily lowering the Power Limit all the way to see if it prevents your PC from crashing during intense gaming moments
If you are comfortable with tuning your PC and your motherboard allows it, you can try "undervolting" your CPU in the BIOS to have it draw less power while retaining the same performance. Undervolting your GPU can also be done within the AMD Adrenaline tuning tab. **WARNING:** *Don't attempt any BIOS changes unless you know what you are doing and understand how to fix any errors that might occur in the process.*
I wish you the best of luck and hope one of these things helps,
YellowRose