If you're insured/can afford it, go on and see a cardiologist. It wouldn't hurt, especially with your apple watch results to show them. 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. Don't let them immediately blame it on stress/anxiety, exhaustion, whatever else. Emphasize how abnormal that episode was to them and push for yourself.

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 in PDF files.

https://www.amazon.com/dp/B07RQW6SD5?psc=1&ref=ppx_yo2ov_dt_b_product_details

I’ve also had health related anxiety. Are you able to exercise? Do you feel worse after exercise? If not, then you’re likely just fine. You can take an ekg and get an automatic interpretation with this device: https://www.amazon.com/KardiaMobile-Personal-Device-Heart-Monitor/dp/B07RQW6SD5/ref=dp_prsubs_1?pd_rd_i=B07RQW6SD5&psc=1