Aw, I totally get the worry, especially kapag first time nangyari yan! A few of us moms noticed the same thing, sobrang stiff ng baby pag intense crying or gas, legs and arms ganap locked, parang statue for a few minutes tapos back to normal. Nakita ko rin na marami sa cicle ko na nag-experience ng ganito around that age, and honestly, most of them said it stopped after 2-3 months na.
What I've heard na tumutulong is gentle massage sa hands at legs pagkatapos mag-calm down, sometimes they just get all tense kasi walang alam kung paano mag-express ng emotion, you know? Some moms also noticed it happens more when baby is overtired or frustrated, so try observing if may pattern ka. That said, since it's the third time na, worth mentioning it sa pediatrician mo just to be safe, hindi bad thing kung mag-check lang siya, plus peace of mind for you mama!