Azure functions Http triggers getting down and throws 503/502 and sometimes even requests are not reaching to Http trigger

We have a azure function app(App service plan) in which multiple http triggers are present. Sometimes functions app gets down and started throwing 503/502 and after restarting 2-3 times it starts working.
Sometimes even request are not reaching to the http trigger and request gets stuck.

Is there any way to find the root cause of the issue or any telemetry why it is happeing.