The above is a common sight if you have a moderately successful website on SiteGround. That’s the screen that SiteGround replaces your site with when you exceed your account’s resource usage. It’s something I’ve experienced regularly over the past 3+ years with dozens of customer sites.
Basically, all shared hosting accounts on SiteGround have a limit for the amount of CPU time and RAM that you can use. SiteGround will send you 1 warning when you are at 90% of that limit, and when you exceed the limit you will get another email notifying you that your site has been temporarily suspended.