can someone else relate?

can someone else relate? so my problem is when im thinking about a certain specific word or phrase i want to say to someone else and when i go to say it the word just doesn't come out of my mouth. for example: i see a person in the distance holding the door open. (the doors at my school automatically locks when closed) and in my head im thinking of saying "thank you", when im in a close proximity of them i then prepare to say "thank you" but those 2 words won't come out when i try to say it so i double down and give them either a handshake or nod. has anyone else regularly experience this?