The “simplest” thing you can do is just try to be aware of it and consciously stop.
…but I know that’s so much easier said than done.
I’m going to get botox injections in my jaw muscles. Its an effective treatment for TMJ apparently. Might be something worth looking into if you’re getting to the point where it feels like your teeth are moving around from the clenching. A dentist or plastic surgeon can do the injections for you.