Fear of having a cardiac arrest.

I have had fear of having a heart attack since last 3-4 years since i witnessed a heart attack. I had done echo multiple ecg and other blood test in the last few years and everything was normal. But recently after seeing reels of people at the age of 29-35 having cardiac arrest while just sitting or doing nothing, my fear has come back. My focus stays on my heart beat, and I have stopped playing sports and exercise cause my heart beat elevates. I am 6'1 and 82kg . I even sometimes panic while sitting if i feel any pain in the chest area or heavyness. I have been smoking since the past 1.5 years just 1 cig a day 4-5 times a week. I just want to understand if I might have a cardiac arrest anytime?