I just turned 25. I have the exact same issue as you. It gets more intense in the more unfimiliar or stressed situation I am. I can see the word in my head but I cannot pronounce it. I try to come up with a synonym or something or just be like "let me think" so maybe I can say the specific word later. I have no idea how to solve this I am in stutter therapy now but thats just focussing on more confiddence or something. Idk anymore.