Anyone else out there had similar experiences?
Any advice?
Anyone?
Bueller...? Bueller...?
My concern is that it seems like a natural inclination for me and will only serve as a roadblock on the progress of insight.
Sounds intense, but since this is something you think is going to be part of your practice (and to me it's normal to have these kind of jolting surprises to which a fear response is sort of predictable in older-than-young-kids) I'd let it go by considering it as "nothing special, re-attend."
[edit: I know attention and energy around the heart can be unnerving. Again, to me, this reinforces why stimulants like coffee are not taken to support wakefulness in meditation (not that you do! I just re-iterate that point often), and why a receptive alert attitude is well balanced by a timely "nothing special" attitudinal approach, too.
You can also try to think about the heaviness of the hands and feet and sometimes that can give release, but it's useful too to just abide calmly and observe when energy/sensation is staying in the chest, just "Okay. Nothing special".
And I'm a fan of applying long, slow, gently breathing to help the parasympathetic brain soothe a fight-flight (anxious) sympathetic brain reaction. The thing is if the stronger perception of heart beating continues, one just continues to relax, consider it all as "nothing special", have long slow breathing and not getting attached to making/not making the sensations change. One is staying with them as they are, watching them or moving attention if needed to another part of the body like the anapanasati spot at the nostrils or to the back and base of the head, while still applying a calm, long breath to just balance or soothe anxiety that may be circulating or starting to fire up in the brain. Makes sense?]