Can i reset UNO when PIN is LOW (randomly 24/7)

My Arduino is connected to the relay 24vac thermostat through the latch relay and the read pin of Arduino.

The problem is, sometimes I need to turn this system off and on.

The time when family members are at home is variable.

And I want Arduino to be aware for himself when the 'pin' connected to the thermostat is not active.

yeah, i hope possible to resetting arduino himself at that 'time'.

Can I do that automatically with just a few lines of code?

or can i expect any good news?

Show us a good schematic of your circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.

If you ground the Reset pin, the Arduino will reset. There are various ways to arrange that.

Does the mystery pin actually go "LOW" or is it left floating? If it actually gets pulled down to Ground, just jumper it to your Reset pin and the Arduino will be held in reset whenever that pin is LOW.

Thanks all.

I can realize that it's not as complicated as I thought it would be.