This is a manufacturing defect of exynos 9611 soc and a quality control fault of Samsung They had provided free repair to many users but now it has become widespread https://r2.community.samsung.com/t5/Tech-Talk/Auto-Restart-Brand-solution/td-p/10333335 Follow the above steps in the post, if they deny, then ask for discount and be adamant that the update has damaged your phone, tell them you will file complaints in consumer forum
We acknowledge your query and apologize for the inconvenience caused to you and will surely assist you regarding the same. We'd like to inform you that your device is eligible for Andriod 12, however, due to some technical issue it is delayed and the concerned department is working on it. However, Providing a continued great experience to our users is our first priority. So we would request your patience till any further notification and check your device update section from time to time to check for the update availability. You can also check for the software update information for your device in your Samsung Members app.
