Hi,
Try starting the phone in [https://www.samsung.com/in/support/mobile-devices/safe-mode-on-samsung-phones/|safe mode] and check if it starts OK.
If it does then a ''downloaded app'' may be the cause of the problem.
You will need to uninstall each ''downloaded app,'' one by one, and then test the phone in normal mode between each uninstall to see if it starts OK or not. When it does the last downloaded app that was uninstalled was the culprit.
A ''downloaded app'' is one that you downloaded and installed on the phone and wasn't pre-installed on the phone when you first got it.