Hosting resources overload

Hello,

I would like to hear your opinion about wordpress (latest) and hosting’s CPU and processes overload.
Here is the story. First, admin becomes very slow, two months later publishing post becomes very slow. Then, last time everything crashes after post publish.
CPU and processes were to high and hosting automatically blocked access to the database.

Turned off all plugins and switched to default theme but resources are still high.
What can be the problem?

Thanks