I know I've given you this advice before as you have asked this now many times here on the anxiety forum--- you seem to know on some level that this is anxiety driven. The anxiety is what you need to be talking to your doctor about. Not heart issues as you do not have any (all tests indicate this). So, the root of your problem is your anxiety and that is what I'd work on so that you can overcome this fear and begin to enjoy life more. good luck
I know for myself lack of sleep can cause my anxiety to rise! Excersize is one of the best things for anxiety so I would say containing to do so is a good thing! Something that happened while you were driving could have stressed you out enough to trigger your anxiety on top of the lack of sleep...or even if you were simply thinking about things that stress you out. You can always test it and get a good amount of sleep for a few days then force yourself to get lack of sleep and see if it happens again.
And I used to feel them whenever I did workout but whenever I started to workout more and more they have stopped all together