THANKS FOR CHOOSING HEALTH CARE MAGIC,
generally,fever wtih chills ,shivering is seen in malaria
where the patient gets high fever
which drops after some time and the patients starts shivering
fever with chills and rigor occurs in urinary tract infection
did you get his urine tested?
if all these are ruled out
check for hyper and hypoglycaemic conditions by frequently monitoring blood glucose
levels which may the cause of shivering
check if the shivering is decreasing after taking some food.
fluctuations in blood pressure and sudden low bp may lead to sudden fall in temperature,loss of consciousness
get his bp levels checked
hope i answered your query
feel free to contact me for further queries