Sometimes, shyness is terrible feeling. For me it is like I know how I should't behave, but I cannot change it, so I do just opposite. The pressure is even bigger if I am overthinking over my "wrongness" in the moment where I see other people having no problem with being spontaneous.
I hate it most when i see people behave wrong and I'm too shy/scared to tell them off, I'm just happy that they leave me alone