PC randomly restarts out of nowhere

As title suggests.
Coming home the other day I find my PC started to restart out of nowhere, with no warning before or errors afterwards.
I haven't changed anything and haven't had this problem before.

Any suggestions on what to do?

Device specs:
Processor Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz 3.60 GHz
Installed RAM 64.0 GB
Storage 233 GB HDD ST9250315AS, 112 GB SSD OCZ-VERTEX2, 466 GB SSD Samsung SSD 970 EVO Plus 500GB
Graphics Card NVIDIA GeForce RTX 3060 (12 GB)
System Type 64-bit operating system, x64-based processor
OS Windows 10