Baby shivering? 😥

About a week ago I noticed my daughter have a little shiver like when you drink something cold or something. I'd never seen her do it before. And it only lasted a second or 2. But then later that same day she did it again. She wasn't cold and I know right now they are too young to shiver when cold anyway. It literally was a quick little "shiver" movement. Like literally "a shiver down your spine".

Since then she's been doing it about once or twice a day (maybe more that I dont see?). She's not doing anything specific when it happens, usually just sitting in my lap. It doesn't appear to be related to muscle control and its different than the moro or startle reflex. Is anyone else experiencing this or know what it is/causing it?

I tried Google but of course its all scary and concerning results. So now I'm a bit concerned why she has suddenly started doing this. We have our 4 month check up this week so definitely will ask the doctor but wanted to see if any of you mamas knew what this is?

Thank you. 💗