How do you open up about childhood traumas that you struggle to remember?

Hey guys, I’m a 20M and have my first appointment with a psychologist in a few days, they’re specialised trauma and work for a practice that only talk to under 30s so I’m not doubting their credentials on dealing with stuff like this,

My question;;;

Without getting into it too much, I have a lot of childhood traumas that I even struggle to remember at all or details, sometimes it comes to me out of nowhere and sometimes I forget about it for months and have no recollection.

I’ve mainly been noticing how it’s been affecting me in social situations which I have been writing down so I don’t forget that as well

An example is I get really on edge when being around people that all resemble my dad which unfortunately is just a middle aged white dude lol.

I’ve been getting better at noticing things like this but I don’t really know exactly why I feel that way because I forget so much of what has happened.

I know he was abusive and there are very specific things I can remember but on a broader scale my brain has blocked it out

Looking for any advice or any tips on what to expect in the coming journey

Thanksss