Page load TTFB problem

I have a problem with loading pages, it often happens that TTFB is needed from 4 - 8s, but the next time I load it for 300ms, you don’t know where I should look for a problem?

I have most of the things in the cache, these are 2 sql queries, which are very fast according to the log …

Thank you

There are plenty of reasons for this but without knowing your setup, it’s difficult to know what exactly might cause it.