Hello, I can certainly understand how frustrating it is when your phone is constantly rebooting. It seems you have tried all the troubleshooting available here: Samsung phone or tablet reboots repeatedly.
The next step would be a service repair. You can use the following link below to request service in the U.S. https://www.samsung.com/us/support/service/ or by contacting customer support at 1-800-726-7864.
