Notebook shuts down out of nowhere after installing Windows 11 - ASUS X571GT

the only reason I know of that will shut down your system without any warning, is when your CPU gets too hot. The CPU has a fail-safe mechanism built within the CPU itself that will protect the CPU by shutting itself off, if it happens to get too hot. Being that you are using a laptop, that doesn't have a whole bunch of ways to receive cool air compared to a desktop, it's highly likely I may be correct here. A lot of people feel that since it's called a "laptop" it makes sense that you can lay your laptop, on your top lap. But this isn't a good idea since most laptops have their cooling vents under the laptop, by placing a laptop on your lap you effectively block those cooling vents and guess what happens? The laptop begins to over heat depending on how long they keep it on their lap. Another big mistake people do with their laptops is use it in bed or on a couch. Both of those platforms are a bad idea due to the fluffiness of their surfaces which can also block the critical air vents under the laptop. You need a level hard surface to lay your laptop on so there is ample cool air below the laptop for the fans to be able to suck into itself to cool it's CPU down. never place the laptop on a soft surface so that the air intake or exhaust vents can be covered. that can cause your laptop to over heat and then shut down with no warning what so ever. Another issue that can cause this is a loose battery or failing battery if it only happens when the AC power adaptor is not being used. If your battery is removable from the outside, the remove it completely, the re-insert it again, being sure that the locking mechanisms latch properly to lock the battery in place. If its an internal battery then it's probably not loose its probably more likely to just be failing on you. if the problem is not an overheating issue.