‘Oops not found’ and severely slow

Good morning,

I have an issue with my existing WordPress installation. It seems that whenever there is a sudden and large influx of visitors (it seems anything above 200 people) then my website becomes very slow, unresponsive and eventually throws up ‘Ooops, page cannot be found’.

Scenario:
– I publish a story (it’s a news website)
– A large amount of visitors head to the website
– If I then try to make a slight amendment to the story and hit ‘update’, it goes extremely slow
– Eventually throws up ‘ooops page cannot be found’
– Cannot load the website if try to load the website afresh

At first I thought it was a server issue, however, it has emerged that the problem only exists when logged into the admin panel. If I open up the site in a private tab it loads absolutely fine and fairly quick.

I’m hoping someone will be able to point me in the right direction as to why this is only happening when logged in. If it was the server not being able to cope with the load/visitor numbers, then the site wouldn’t load perfectly fine in a private tab – or for the hundreds of people on the site.

Regards