I see what you meant. I rarely speaking out loud, but speak in mind a lot. I read from Lee Lovett to stop trying to rehearse my speech in mind just moment before saying it, and it somewhat helped.  Ironically experiencing more blocks after moving here made me realise some things. I realised that I had almost zero awareness during the blocks, like a blockout period. I tried to take a breath and relax, then realised I was never able to. Everything happened continuously without my control like a car crash, and I was just left with tense sensation at back of my neck Thankfully now I sometimes become aware, and can feel the tense sensation much earlier than before. Awareness make consonant block usually beatable, but vowel is a little harder. I cope up with synonym or by leaving the initial vowel out.