TDP is not power consumption, it's a thermal profile ! That CPU is quite a bit more power hungry. Also a 2080Ti will pump a bit more than that on full power... And you have to add the motherboard itself, and everything else..
And again, that's absolutely symptomatic of a power issue. Even a faulty RAM chip would actually result in a BSOD. Complete and brutal reboot is a PSU fault, or VRM fault. There can be multiple causes but usually the first remedy is to throw the PSU into a recycling bin, and get a fresh one. Next is CPU cooling, might be a thermal spike, that also can result in a cut off if really, really it's going way overboard..
A 750W PSU would be perfectly fine for that setup if that were a good one (Seasonic for instance). I have seen a lot of off-brand PSUs that did not deliver what they advertised (and even one or two that blew up, with flames..), also faulty capacitors is a thing.