If you use my trigger in your automation, that will work as expected provided the interval is an integer factor of 60.
Alternatively:
trigger:
- platform: time
at: input_datetime.ora_inizio_avviso_temp_bassa
- platform: state
entity_id: automation.ENTITY_ID
attribute: last_triggered
for:
minutes: "{{ states('input_number.frequenza_avviso_temp_bassa') | int }}"
Rest of the automation as before.
This will trigger at the start time, and whenever it’s been x minutes since the last trigger.
Not sure what will happen if you restart HA or reload automations whilst it’s running.