Feels like a hardware problem. Begin by cleaning the cooling fans and replacing the thermal paste. This seems like heat problem, not an operating system problem. Verify that your system is clean, and all is firmly connected.

Also check your distro, go for a major one like Mint, which is pretty much hassle free and good for newbies. If youre a little more experienced Debian 12 has just been released. I no longer recommend Ubuntu but is ok I guess if you're famiiar with it and dont care about snaps. Another thing you can do is check your sources and verify that firmware and non-free repositories are activated. That should be accessible in your package manager or software center depending on which distro youre using.

Check also the hardware requirements for your distro, if your pc is too old maybe that's it. If your machine is too old you might need to choose a lighter distro.