What do these emails mean?
LiteSpeed has a feature that will attempt to temporarily address 503 errors by restarting the webserver when many of these errors are detected in a short time period.
However, LiteSpeed recommends that if this is something that happens often, you may want to consider disabling this feature and address the underlying issue with the application experiencing the problem.
You may disable this functionality from the LiteSpeed Admin panel as shown here.
For tips from LiteSpeed on identifying a 503, you may use this resource.
Here is LiteSpeed's knowledgebase on this feature as well for more details.