My solution is to take a deep breath in and start again. Sometimes when the words are too big or compound, be ok with the fact that you are going to say it very slowly and it may sound a bit weird to others. That's fine (for ex. Detective -> Dee tech ti v). It just became easier for me with age (with age came the calmness and the ability to detect these blocks and not panic.) Another thing you can try is diaphragmatic breathing (and talking 1 word at a time) in alone time, for problematic days. It's important to mention that this works well on some but doesn't work at all on others.