One of body language: he is in a state of anxiety
Close-up of body movements: his hands are under his hips -- sitting on his own hands.
Behind the scenes: When people express their feelings freely and unreservedly, their hands usually fly around unconsciously, with their hands under their hips and sitting on their own hands, which means that they are trying to control themselves, so as not to blurt out what they should not say.
Response tips: praise him as a sweet baby and so on. You can also use relaxed body language to soothe his uneasiness -- extend your arm behind the back of the chair, put on a look of contentment, or give him a surprise hug from behind.
He is not necessarily hiding something unseemly, but is afraid that what he says will ruin the whole situation or atmosphere - in fact, many people have this habit since childhood. This also indicates that he is worried that his next words and deeds will cause others' displeasure. When he feels your peace and tranquility, he will also relax, and the insecurity will gradually disappear.
Body language 2: He has something to say
Close-up of body movements: he leans forward, his shoulders fall down, and his eyes float over your head.
Behind the scenes: Many people will make this body language involuntarily when they decide to tell the truth. This gesture represents that his mind is in a submissive and obedient state, and secretly hopes to get your understanding. However, you don't need to make a final decision immediately -- what he is ready to say may not be the thing you are most worried about. Maybe he just needs your help.
Response tips: You might as well use a light tone and start with questions such as "You seem to want to talk to me", then shut up, leave some time for him to consider the wording, and wait patiently for his response. Never stop asking like turning on the machine and turning off the gun, but "steal" his chance to speak.
If what he wants to say is not what I'm sorry for your loss, of course he won't hide it in his heart for too long. If he stops talking more and more frequently and swallows his words again, the truth of the matter is likely to annoy you very much - at this time, you'd better be prepared mentally, otherwise once you mess up, you can't calmly think about the way to deal with it.