1st solution reduce php_max_excetion time
60-30s (60 producation value) my casuue i set it 300secs or 5 minutes dont; use it.
60 seconds fine
2nd solution: reduce php_max_memory_limit
don;t leave it as 512M reduce to 64M or even 32M (ideal 64M to 126 but yoast seo plugin needed much memory you may get fatal errors.
tip: reduce sitemap count 500-1000 instead of 5000.
3rd solution: reduce php worker process,
in case you are not getting max worker reached error in php fpm log
set to ondemand, don;t go for dynamic, static only for dedicated resources high traffic websites.
4 Switch to dynamic pool manager from ondemand
in the ondemand every resquest process has to spawn and destroy after reaching the idle timeout.
4.a increase pm. process idle timeout
before switching ondemand try to increase pm. process idle timeout (it consumes memory while in idle).;
My case not still not fixed but reduced cpu load 20 to 1.3 for 2 cores 4gb ram. with Cloudflare cache every thing rule (not recommended) have to dig more update this accordingly.