pc shuts down every now and then

My PC freezes in any running game, from time to time. I did stress test for GPU and CPU. For the GPU, I did not receive any error, but for the CPU, I received a thermal throttling, which I fixed with the orientation of the fans. The case is always open, I have the feeling that it heats up a lot because of the video card, even though the card stays at 80-81 degrees at maximum speed, either with the case closed or open. Sys specs : Asus ROG MAXIMUS z690 HERO (bluetooth does not work for this motherboard),12th Gen Intel(R) Core(TM) i9-12900K (24 CPUs), 3.2GHz, NVIDIA GeForce RTX 3090 Ti, 4 x 16 GB (6000 c 36), SSD Samsung 2 TB 980 Pro M2, EVGA Supernova 1000 G6 Plus FM, Cooler ARCTIC Liquid freezer II 360, Lian Li PC-O11 Dynamic EVO Tempered glass case. If you have any suggestions it would be appreciated.