If your phone continuously restarts or gets stuck on the Xiaomi logo screen, first try a by pressing and holding the Power button for 10–15 seconds. This will not erase your data. If the problem persists, perform a hard reset via recovery mode as described in Method 1. A hard reset can solve many software issues, but if the boot loop is caused by more serious problems like a virus or deep system corruption, you may need to flash the device using Xiaomi's official flash tool.
A hard reset (also known as a factory reset) on your Xiaomi Redmi S2 will restore the device to its original factory state, erasing all local data, apps, and settings How to Hard Reset XIAOMI Redmi S2