Why does my baby flintch and how to correct it?

My baby has always been smart, from the womb...lol. He's 5 months now very active. He acts like a 2 year old for sum odd reason although he cant walk, talk, sit up, crawl, etc. Anywho all of a sudden, anything I do he sumtimes flintches and it makes me sad to c my baby afraid! If I yarn, If I come out the blue and say awwwwww. I didnt kno babies get scarred like that unless sumthing happened. Nothing happened though.Now once way bac wen, i ws looking @him in his crib and im not sure if Iyarned or was about to say awww u r socute but wateva i did he flintched and start screaming crying and i started crying cuz i saw him scarred and i was like wat i do? Idont think this is the case b/c I have him crying laughing wen we play pic a boo. he loves it! but sumtimes he jumps...he doesnt cry afterwards but i pick him up cuz it makes me sad.Maybe its sudden loud noises. idk. help! How to correct him cuz i didnt kno babies get scarred ps dont judge me 4 not knowing, i didn't have many babies growin up to know this.