503 error code

I recently bought an expired domain with about 354 backlinks, setup on WordPress but alas! started encountering the error "508 insufficient Resource" even after getting in touch with my hosting support. the issue is resolved and after a few hours, the problem reoccurrences again. The website...

As the title says which is the best way to stop too many connections to the file wp-cron? I am using Wordpress and I would like to know if there is any plugin I can install to prevent attacks such this. Or any other way to with changing permission. I get 503 error and looking for a way to stop...