Hyperactive startle reflex? (If that's going on of course!) I'd just use what I saw--what made you call it jittery? Flinching at sounds? Crying when stimulated? Whatever specific thing that made you think jittery! Of course that is my totally inexperienced, idealistic, student-style opinion.
fine tremors of whatever is tremoring. upper or lower extremities. does it stop if you hold the extremity? irritability. incosolability. i have written jittery in the chart before too. now we have all computer charting w/ a bunch of little check-off boxes.
In our babies, we commonly see this when mom was a poly-sub abuser; once you see it, it's hard to forget! Try this: Take your arm and hold it out in front of you flexed at the elbow. Tense all your arm muscles very tightly and then 'jiggle' your arm very quickly- like muscle tremors? Like you've been drinking too much coffee? That's jittery. Often you'll see this in a newborn who has been exposed to crack or cocaine (at least, this is what we see a LOT...we get a lot of cocaine abusers in our area). Another way to demonstrate this is to tense all the muscles in your neck and jaw until your head starts to sort of vibrate and shake? That's jittery. In a baby, you'll usually see that they startle easily (sometimes for no reason at all, ie, no sound or stimuli; just happens out of the blue or when they get extremely agitated) and begin flailing their arms and/or legs, and then the flailing starts to a sort of shimmy-like muscle vibration. It's really not hard to spot when you see it, because normally babies don't do this. ;>)
You can call it "jittery", it's a legit term, and everyone knows what you're talking about. It can also be caused by hypoglycemia, esp. in infants of diabetic moms, including gestational diabetes. VERY important to check blood sugars on a "jittery" baby.
It can also be caused by their immature CNS and is very normal in the first few weeks of life. My mom was convinced my first child was having seizures. She insisted she go along to her two week check-up so she could talk to the pediatrician. She was thrilled to find out she was wrong .