Hello palakfrombaroda,
Thanks for trying a reinstall of iOS. Next, I recommend restoring the device to factory settings, and reinstalling a fresh iOS, and testing without any personal data on the device.
As mentioned before, please ensure you have a backup before trying this step. How to back up your iPhone, iPad, and iPod touch - Apple Support
Then, we need to use iTunes to restore your device because we need iTunes to help install a fresh version of iOS again. But this time, we are erasing the device and making it like it was new out of the box. This help article will assist you to complete these step: Restore your iPhone, iPad or iPod touch to factory settings
Once erased, ensure you set the device up as new, and do not restore any information from an iCloud or iTunes backup yet. This step will isolate the issue and let us know if it is related to the previous data on the device.
Once the device is set up as new, you will test to see if the phone is still restarting. If this issue is no longer happening, we know the issue was with some data on the device or in the iOS version, which will most likely be saved in your backups. You can manually bring data back using iCloud or iTunes, but do not restore from the backup as you will bring the problem right back in. Once you log back in to iCloud with the same Apple ID that you used previously, all your data saved in iCloud will start repopulating on the device.
This help article has the info to help you get your other data back to your device, whether you have a Mac or a PC. Depending on the info, you may need to use File Sharing, an article linked near the end of the article: Changes in the new iTunes
You can also redownload fresh copies all of your previous purchases using this article: Download your past purchases
Thanks once again and have a great rest of your day.
Thanks for trying a reinstall of iOS. Next, I recommend restoring the device to factory settings, and reinstalling a fresh iOS, and testing without any personal data on the device.
As mentioned before, please ensure you have a backup before trying this step. How to back up your iPhone, iPad, and iPod touch - Apple Support
Then, we need to use iTunes to restore your device because we need iTunes to help install a fresh version of iOS again. But this time, we are erasing the device and making it like it was new out of the box. This help article will assist you to complete these step: Restore your iPhone, iPad or iPod touch to factory settings
Once erased, ensure you set the device up as new, and do not restore any information from an iCloud or iTunes backup yet. This step will isolate the issue and let us know if it is related to the previous data on the device.
Once the device is set up as new, you will test to see if the phone is still restarting. If this issue is no longer happening, we know the issue was with some data on the device or in the iOS version, which will most likely be saved in your backups. You can manually bring data back using iCloud or iTunes, but do not restore from the backup as you will bring the problem right back in. Once you log back in to iCloud with the same Apple ID that you used previously, all your data saved in iCloud will start repopulating on the device.
This help article has the info to help you get your other data back to your device, whether you have a Mac or a PC. Depending on the info, you may need to use File Sharing, an article linked near the end of the article: Changes in the new iTunes
You can also redownload fresh copies all of your previous purchases using this article: Download your past purchases
Thanks once again and have a great rest of your day.