Baby Shivers

Hi mommies. Normal ba sa baby 4-5mos na bigla bigla nalang nanginginig. EBF si baby. As in shake from head to shoulders. Mga 2 beses na nangyare. Iba iba kasi sinasabi sa google. Next month pa schedule namin sa pedia. I just want to know if its normal or should I be worried na. TIA. ??