If you are using hosting from a well-known host, the issue shouldn't be at the host. As per my knowledge, every time an issue was generated due to some plugins.
I would recommend disabling all the plugins, then posting blogs whilst enabling the plugins one by one.
If you have 10 plugins, you disable all of them and start posting with 1 plugin enabled, if the I/O usage doesn't go crazy enable one more and post again, and so on.