I assume this is relatively normal however it is distressing seeing my son in such a state. Over the last few days he is constantly stressing out about choking on things, having things stuck in his throat, not being able to breathe and his heart stopping. Every time he eats something he panics about it being stuck in his throat, though there is no evidence of this. Yesterday while walking the dog he spent the majority of the time stressing that he had fur in his mouth and was quite distressed, even after having a drink and me checking his mouth multiple times. He also has been worried that his heart isn't beating anymore.
My mother just had a tumor removed last week and has been in quite a bit of pain and obviously having mobility issues, and I am pregnant after losing my last bub at full-term, so he probably has a few issues on his mind. I have been offering reassurance, practicing breathing exercises with him and trying to distract him.
My parents recall my sibling and I going through similar stages in our childhood, so just after opinions on whether this is probably normal or something I should be concerned about. He isn't really an anxious kid generally.