ERR_EMPTY_RESPONSE – in a wordpress page: what can i do: how to test the uptime

dear community,

from time to time i get an error in a freshly installed wp-page.
what happens:
i get the following error: ERR_EMPTY_RESPONSE – in a wordpress page:
what can i do: how to test the uptime?

how to find out how often the page fails to load.
are there any tools out there that do some tests.
BTW; i can also have a closer look at the logs.