You could configure Escalation Rules when an agent has not sent the first response within a set time. This could be done under the Admin > Workflows > SLA Policies >Edit >"What happens when this SLA is violated?"-->"Set escalation rule when a ticket is not responded to on time".

You could also configure an automation under Admin > Workflows > Ticket Updates > New Rule

A sample rule looks like this:

When action performed by: System

Conditions: Ticket is marked overdue for first response

Actions: Send email to agent-->Escalation Agent Name

Here is a sample rule: