Randall has been dealing with a lot on This Is Us. After wanting desperately to be connected to his biological family all his life, he finally found his birth father, William, only to discover that William was dying. Dealing with that, his demanding job, and his duties as a husband and father have been putting an increased strain on Randall. At the end of "I Call Marriage," that strain manifested in his hand shaking seemingly uncontrollably while he tried to pick up a glass of water. It was a worrying end to the episode, and these This Is Us theories about Randall try to figure out just what is going on with him.
The biggest worry when it comes to Randall is that the tremors could signify something really serious. Health problems are the last thing Randall needs on top of everything else, but they're also something that can often appear during tough times. Randall is pushing himself really hard, and that inner turmoil is being reflected in his body. The promo for next week, "Jack Pearson's Son," showed the shaking will be a continuing issue, so it's going to be one more thing Randall has to deal with. The promo also seemed to link the tremors directly to how stressed Randall is about William's health, which gives some weight to certain theories about what's going on with him.
Anxiety has always been an issue for Randall. When Randall's hand started shaking, he didn't seem taken aback, though he did appear to be frustrated. The lack of a freakout could imply that this is something that Randall has had to deal with before — it's a familiar enough situation to him that he knows what's going on. Shaking hands can be a symptom of a few different anxiety disorders, especially when coupled with Randall's lack of sleep and nightmares.
Earlier in the season, Beth mentioned to William that Randall's all-consuming drive for perfection had resulted in him having a breakdown years earlier and suffering from hysterical blindness. That made Reddit user DJBAHLER think that Randall could have conversion disorder. According to the Mayo Clinic, conversion disorder is "a condition in which you show psychological stress in physical ways" and is classified as a functional neurological symptom disorder. That means that while the brain is normal and there doesn't seem to be a physical cause, a person can still suffer from weakness, shaking, and vision issues. Conversion disorder is an emotional crisis manifesting itself physically, which does seem to make sense for Randall right now.
But then again, you can't discount that something even more serious might be going on too. Some fans were concerned that Randall's shaking hands might be a sign of worrying things to come, because it's a symptom of multiple sclerosis. MS is a disease in which the immune system attacks the central nervous system and it can result in shaking hands, vision problems, and fatigue — all of which Randall had dealt with.
Parkinson's disease also affects the nervous system and has some similar symptoms to MS, making it another possible diagnosis for Randall. However, despite the fact that tremors are one of the biggest warning signs, Randall hasn't presented any of the other common symptoms so far, like limited movement, weakness of the facial muscles, or difficulty walking. This particular theory doesn't seem quite as plausible as the others do.
It does seem like whatever is going on with Randall is directly related to all the pressure he's dealing with at the moment, and he's dealing with a lot of pressure. It makes sense that it would start to take its toll, even if it's tough to watch Randall shoulder one more stressful situation. Fans can only hope that he'll be OK eventually, and that it'll be sooner rather than later.