i think now and then everyone gets a blank mind, when its all the time yeh it is an issue. but i reckon maybe its because we can be so busy analysing the enviournemtn or how anxious/depressed we feel, and go into ourself and what r bodies are saying, that we become detached from whats happening around us. its not that ur mind is blank so to stay, its just no focused on talking. its focused else where. im quite extroverted person, i love to talk, laugh and be apart of whats going on, but i can be quite introverted at times where i go into myself and i have blank mind syndrome, then i get overwhelmed with this blank mind.
just try not to focus to much on it.
also the more you do, the more you have to talk about. what i find when theres no one talking is just chat some shit like 'im thinking of going traveling for a bit in the summer' then people r like where? u say where then they spout of about where they wanna go etc. people like to chat on about emselfs that is right, but remember we are people and u can chat on about yourself an all. but dont only talk about yourself, or only talk about others. middle road.