I think you're saying that you get stuck in an auto-reply loop where you are sending an autoreply, then someone else OOO sends you back an auto-reply and you get stuck in that loop over and over again, is that right?
If that's the case, you only have a couple of options here:
1. Use Rights Management to prevent the recipient of your email from being able to reply. This requires an admin to enable the ability, then will require sending the email through the Graph API because the Power Automate Send an Email action does not have any Rights Management attributes OOB.
2. Uniquely identify your auto-reply (for example, with the words "AUTO REPLY" in the subject) so that when the other person's autoreply sends you a response, you can filter their response out (Subject--Contains--"AUTO REPLY") from your Power Automate flow and not send them another email in response.