What you describe sounds like health anxiety -constant fear of a heart attack despite being safe-and now it has started appearing around your naps as well. Anxiety can sometimes trigger physical sensations (like chest tightness, racing heart, breathlessness) even during light sleep, which makes you wake up feeling panicked.
Next Steps
This is a common pattern in long-standing anxiety. Practicing relaxation before naps, keeping a consistent sleep schedule, and using grounding techniques can reduce such episodes. Counselling (especially CBT for health anxiety) is very effective in breaking this cycle of fear.
Health Tips
Since you've had anxiety for 5 years, it's important to combine lifestyle changes with therapy for lasting relief. Please rule out any heart condition once with a physician if not already done, but otherwise, this pattern is more anxiety-driven than dangerous.