[CentOS] Apache (httpd) fails to start at boot - Centos 8.1

Just a wild guess, but it sounds like Apache is being started before the
network is online.    Is this host simple static Ethernet or DHCP, or is it
something more complicated like WiFi?

I believe you can set service dependencies with systemd, ideally your
apache service isn't started before the network is online.

If you are using WiFi, running a webserver is a bit ugly, perhaps
configuring Apache to listen to 0.0.0.0 (all interfaces) would be a better
choice?