PC problems – reset/freeze?

For a long time now, my PC has been automatically resetting itself, usually when I close programs or games. Then it restarts automatically, or the screen remains black.

For the past few weeks, my PC has been freezing constantly while I'm using it. The picture freezes and the sound stays there for a minute, then it disappears. After a few minutes, it shuts off.

Does anyone know what could be causing this?

CPU temperature is always normal.

CPU: Intel i5 11400F

GPU: MSI RTX 3060

Ram: 16gb GSkill aegis ddr4-3200

Power supply: be quiet! ATX 600W

SSD: Samsung 980 pro m2

Operating system: Windows 10 Pro