Thank you for the log. Maybe i have already found the reason.
The voltage under "GPU Rail Voltages (avg) [V]" should never go under 11.4 V. It is a 12 V rail and it has a 5% tolerance. But on your system it goes down to 10.267 V. The power supply of your system seems to be faulty.
There a two things, you can do:
1. reseat you graphics card. Power down your system. Remove the card from the motherboard, clean the contacts with a soft cloth (maybe with alcohol) and put it back into your computer. Do the same with the power connector on the graphics card. But without cleaning. Then remove the power connector of your motherboard and put it back. This can remove some oxidation on the contacts.
2. If it does not help, then you should consider to replace your PSU. It is either too weak or it is old and it cannot keep the necessary voltage anymore.
Cheers