One of my sites has a poor pageload speed, and is just plain slow.

Some of my websites are very fast loading. I have my own web server. Most of the sites are fast or very fast. This one is very slow. I have gzip turned on at the cpanel level. I also have all of the files compressed through cpanel. PHP is version 7.3.9, SQL is up to the newest and last one available. WordPress and all of the plugins are up to date. Hummingbird seems to be set up correctly and working. There are not any picture files which are too large. I have built 50 websites using this theme and these same plugins and most of them are fast. This one was at one time also. However now it is slow when updating pages and the page load speed is very slow. Can someone please take a look at this site and see if you can find out what is going wrong? There is a vin query which is putting an error code in the error log every day. I will look into fixing that, but what else can be slowing down this site?