I had exactly the same problem with [link|https://service-xiaomi.ir/%D8%AE%D8%A7%D9%85%D9%88%D8%B4_%D8%B4%D8%AF%D9%86-%D9%BE%D9%88%DA%A9%D9%88-%D8%A7%DB%8C%DA%A9%D8%B3%DB%B3/|Poco x3 Pro turning off|new_window=true] and I found out the reason from this non-English article written by a repairman. The exact cause of this problem is the excessive use of the phone and the combination of glue and tins on the Poco X3 Pro CPU. And the only solution is to go to the repair shop, and the repairman must perform the removal and re-installation steps correctly, and no data will be deleted from the phone.