Yes hello, I am a registered nurse, 49 yrs old, tachycardia, small heart murmur, bronchitis, hypothyroidism, I every now and then only while sleeping never happens while in upright position or awake , jump out of my sleep , yell out like my HEART STOPPED BEATING, I am breathing okay , just feel lifeless, only happens when I lay flat in my sleep, scared me most last night, happens maybe 2-4 times per month