Ugh I’m so sorry to hear that you’re going through this but at the same time I am relieved to know that I am not alone in this issue, as a customer who upgrades yearly and has seen Apple seemingly get worse and worse as time goes on, it honestly feels like a toxic habit to stick with Apple at this point anymore, I suggest you run diagnostics on your iPhone, (I have and the diagnostics seem to come back fine every time) also that you do a system stability check, and or even having Apple do a log collection on your device this can indicate as to whether or not something is mainly either hardware or software since it usually is one or the other. I just don’t get why they claim that they “fixed” the issue with IOS 18.1, it was literally in the improvements and bug fixes list, but seem so blindsided to the fact that people are still going through this and other issues, I understand it can take multiple times to fix something semi decently but they have to have some insight as to what they think it would more a less be at this point, has to be a marketing strategy to get people to buy these iPhones that SHUT OFF without our permission.