Hi guys I just wanted to mention that something similar happened to my S21. And in my case, it was related to the way I charged my phone. So, I had this very long zoom meeting and my phone was dying so I plugged my phone to a USB port extender plugged to my laptop. My phone was charging super slow probably for an hour or two. After that the random shutting down started nonstop. I restarted, clean the phone app cache, nothing worked. I found the solution: Just properly charge your phone! So I just turned my phone off and plugged to my Anker fast charger and let it plugged until it hit the 85% (I have that option on to extend the battery life) And this fixed the problem . Hope it helps!