I have two boars around 2-3 years old and am living in northen nsw (Australia) lately when i pick them up, especially at night they are shivering slightly... ive been taking them inside and it seemed to stop. Are they just cold?
What temperatures are you currently experiencing?
Has there been sudden changes downward?
If they are used to higher temperatures, then they may well be feeling too cold.
What you can’t do though is subject them to sudden temperature changes - so you can’t bring them indoors and then put them back outside again as it’s potentially too much of a change and can cause illness.
If it is colder then they are used to or temps are fluctuating outside then bring them indoors (and keep them in) so they can be kept in constant temperatures; or ensure they have plenty of cosy hides and plenty of hay to snuggle into