I'd post this in the pregnancy forum as not a lot of people come to this forum and there are lots of great moms in the preg forum who can help you.

Hi mommee2b

this sounds a little bit like the moro reflex

if the baby has a sense of falling or not being supported, the arms stretch out to the sides, and the legs stretch out full length and baby clutches his/her fists, as if trying to grab hold of something. - just like being startled. This is normal, and all babies do it.

The same reflex is found in baby monkeys - another reason they think we evolved from apes.

Getting upset and trouble breathing is not part of this though. Sorry, hope you can work it out.

Best wishes, sandy