My author site The Last British President has been suffering from extremely long load times and time-outs recently, sometimes with 404 and other error messages, which is a serious problem for any website and a complete turn off for visitors.
I'll point out that I'm on shared hosting for the site, as are this forum and Compufix.
The problem at hand was 100% physical memory (out of 512mb) usage and I/O usage, as per this image:
My first port of call was the plugin section, so I disabled them one by one, but this made no difference at all.
Then I went to the image section and deleted all unused images and resized some to more manageable sizes - no difference.
I also changed the memory limits in the wp-admin-php config - no difference.
Finally, I managed to get onto my hosting company in the US, Godaddy chat, but they had no idea what the problem could be. Helpful but dim, finishing with 'have a wonderful day!'
I then made a cup of tea and began to realise that the problem was intermittent with spikes all over the place, as per these images for the last 24 hrs and 7 days:
I then tested with GTmetrix analyser (which Godaddy uses also) and the site was taking 60s to load, but I couldn't see any errors as such.
Google Insights is also a very good analyser and comes up with much better suggestions.
I then carried on with my Googling, and on Quora, stumbled upon a post where bots were mentioned, so in a last ditch attempt (prior to resetting the entire website), I changed my cPanel password that I'd left unchanged since installing WordPress and designing the site.
Since this is the only change that has fixed the problem, I can only assume that a bot of some kind was strangling the site. I may be wrong, but that's my conclusion for now.
Very useful information if such a pestilential nuisance should ever hamper this forum.