How do you identify your triggers?

Hi, seeking advice in the hopes of being able to handle my relationships better.

How do you identify and communicate the things that trigger you?

For me, I can realize that something - ex. a particular sound my housemate makes - reminds me of someone else. But I don't know if I really want to ask them to stop making that sound. It kind of helps that I hear the sound from somebody new, not the person I went through all the trauma with.

Also, sometimes I don't know how to communicate that something is triggering me because I'm so overwhelmed with the emotions in the moment that it's happening. I just know that I feel really unwell and I need to take some space from the situation.

Sometimes it's hard to describe because it's like a whole social situation is triggering, and I feel like the people in it would not listen to me/believe me about why.

I am really trying to practice regulating myself better and being aware of my emotions and triggers and reactions. It is really healing for me when I've been able to do that. Any advice or thoughts would be appreciated. Thank you for reading.