To me, 60 seconds suggests a timeout is expiring. For example something configured to call to something via a network connection, but it doesn't hear back from the remote end so after 60s it gives up and continues.
Some things to check: if there are any additional plugins installed? If there are any non-standard authentication methods enabled? if using an additional theme is this configured to do something special for login?
Your browser's developer tools may be able to help (for example: Network Monitor in Firefox) by showing if it's the resource /login/index.php that's taking 60s or something else.
On a CentOS 8 server with 2 GB RAM with no other load I'd expect the login page to load within 2 seconds, with no OPcache, maybe 5 seconds.
If you do see debug info please share it, it may be relevant.