First, just want everyone to know that because one person discovers something it doesn't mean everyone posting has that problem. Just responding to someone who has reappeared and is posting again that everyone has the same vitamin and mineral deficiencies, when clearly we're all different. So don't go blindly adding nutrients that can be a problem in that they can interfere with the proper amounts of other nutrients if you don't actually need them. This issue disappears for awhile and then reappears in its same form. Second, try completing your workout and see what happens. You've been told you have no heart problem, and this forum is full of people who think they have a heart problem who don't. Anxiety mimics those symptoms. Complete a couple of workouts and see if that doesn't relieve this episode when everything works out fine.
try going to counseling I have the same issues as you and I have gone to many doctors especially for my heart because of fast heart palpitations. Every time I go to the doctor everything is normal. So I think it could be your anxiety try talking to your doctor about it or try seeing a counselor. The doctor can prescribe you medication, but in my opinion I would not take Anxiety medication they made me feel worse I did not want to do anything but lay in bed and it increased my heart palpitations. It just depends on you everyone is different I am currently taking natural anxiety pills and it has nothing but herbs it helps me way better then the chemicals doctors prescribe. That is just my opinion also try chewing gum when you have anxiety I mean that helps me. Also research different anxiety meditations and stretches they will help you can find many youtube. When it comes to counseling they give you behavioral therapy such as the breathing techniques and what to do when you have an anxiety attack. Exercise is a good way to help with your anxiety so try to keep that up. I hope this helps I have been going through it for years so I know how difficult it is.