Mind going into loading mode

[Masson]

Hey , I have this problem that when I'm around some type of people I just feel mind-blocked and there is literally nothing going on in my mind in that time. I have people to whom I'm completely myself and don't care what I do or say in front of them but then there are those in front of who I just can't be myself and I just say basic stuff like some kind of programmed robot.
I know its a mind-block because I can feel it when I'm around people , but I have days in which I'm all myself no matter who I meet or what I do and I just don't know what triggers that.
I've tried to meditate , relax more , listen to all sorts of music , do sports but nothing seems to help. I'm not the very talkative type , I like to be the listener but when the time comes I'd like to actually enter in a decent conversation without problems , also I am not a shy person so that's out of the way.
Is there anything I can do or use to just clear my mind and be myself ? I thought that I could have some kind of defecency of something because I saw that the lack of some vitamins can lead to anxiety and other issues , could my problem be related to that ? Thank you.