I can’t get angry like ever and I hate it

For some reason for the past 10+ years I(32M) have not been able to feel Anger, more or less express it especially during Arguments. Instead I just freeze up and become extremely timid, and even if I have something to say I can’t express it because I just don’t know what to say at that moment, and only later I finally have things to say when I am all by myself and reflect on the Situation I feel like I should’ve said this or that.

I have a hard time establishing boundaries because of all of it and become a people pleaser instead.

TL:DR: I can’t express my Anger, what do I do?