EC2 Instance Reboot Problem - The Name Server Record and the Public IP Changed Automatically after EC2 Stopped for a Month

you can find from

Route53 > Navigation > Hosted Zones > select your hosted zone > details > hosted zone details > name servers

Thanks sdtslmm. But these were the outdated details. When I nslookup the hosted zone under those name servers, the result is that they could not find the hosted record.