I know it has been a long time (~20months) but I thought that I would share with you that those "fits" inutero have continued into infancy and now toddlerhood. At 15.5mo, it still happens from a few minutes to a few hours, from a lip to a limb, to his whole body. These are with normal temps and not in a cold environment and goes seemingly unnoticed by him as he continues his activities apart from frustration with some slight discoordination.

His blood glucose was done during an episode at KEMH when he was a newborn as they were highly concerned by his shaking. That episode begun in the nurses arms as we were in the testing room getting a blood test done to check on his jaundice levels. His glucose was slightly low but the nurse and the pead both agreed that it was not low enough to cause that type of a response. He did have bad jaundice though but that was also not placed as a cause. I think that with the avalanche of issues coinciding around that time and beyond (plus my lack of interest and observance of my child at the time due to PND&A which resulted in him being taken into care temporarily) his shivers went unrecorded and forgotten about for some time. They were noticed by myself and others during this time to varying degrees but they were just brushed aside as something a bit weird.
Now that it has been going on for so long (and with me having noticed very well for several months now I do not have PND&A) and chatting with others about it and having them tell me what they have noticed, I am very concerned.