If you're insured/can afford it, go on and see a cardiologist. It wouldn't hurt, especially with your apple watch results. They'll most likely give you a Holter monitor, echocardiogram, and/or a stress ekg test. Very standard workup that's not an inconvenience and helps rule out alot.
If you're particularly worried, you can get a Kardia device that can help you see if your heart is in a weird rhythm when you feel these episodes. I use it when I feel my heart rate spike inappropriately and you can send the readings to your cardiologist.
This watch is specifically made to track sp02 by the second..
If you get it Save all the packaging and return it afterwards if need be.
If your oxygen levels fall below 90 while sleeping and you have a increased heart rate from adrenaline response then odds are you have some form of periodic breathing. Mine was hypopnea breathing. And I have a idiopathic cheyne stokes respiratory back sleeping. This watch won't show rera breathing and uars breathing awakenings. But those are rare . Most heavy people have obstructional apnea .. and most past opiate abusers have central apnea.
A sleep study is your next move .. or just buy a Apap machine for 700 bucks and use Oscar sleep software afterwards.
Getting a echocardiogram would be a good idea you could have a bicuspid valve and or some other reason why your heart is beating so hard. I have aortic regurgitation from lifting heavy weights. It has improved with training light and treatment of my hypoxia..
If you need help with diy APAP lmk , it's not dangerous or hard to do..
Being at your size and with panic issues is a few check marks for apnea.
I had no idea I had it.
You can purchase this watch from Amazon and check your heart rate during your sleep It tracks by the second.. It will also track your oxygen and if your oxygen is dipping below 90 or so with an increased heart rate prior to an arousal when you're sleeping then that's a good indication that you have some sort of obstructive apnea going on in your throat from your weight or even a breathing difficulty while sleeping like I have called hypopnea..
If after you buy this and everything looks normal or if you're unsure you can contact me and I'll help you out and then you can just return it if you're an Amazon prime member no harm no foul..
If you do have sleep apnea your body will not be able to lose the weight is easily until you get it treated.. your hormones will also be all out of whack. you only make testosterone when you're sleeping deeply and properly. that is your body's only way to build muscle and burn fat.
Good luck and I'm just putting it out there by any means I'm just trying to help