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:
