my son was the same b4. Well,I think it's sort of personality. Can be improved but not big change. Find a happy learning kindergarten for him. It helps!
Don't worry. 無人怕羞得過我個女,even 見到D一個月見一次的親人佢都會哭到不停. 朋友來我家又哭不肯見人,每次去人地party 必哭即走所以有時唔帶佢去。this prb lasted till she was 3 yo, from then on, not too shy, won't cry and will answer questions from strangers.