Strong heartbeat, heavy breathing and burning body

[Flywithme]

I never succeeded at WILDing. I went this far at three attempts: On a morning, at sleeptime and at around 4 A.M. after waking myself up after 6 hours of sleep. I try the WILD technique, I stop any movement. I never get paralysed, however, after, maybe, 20 minutes, I feel my whole body burning me, my heart starts going off extremely loudly and my breathing gets very heavy (I try to control it and slow it down though). The whole thing lasts around 30 seconds, and after that everything is back to normal, nothing changed, reality check: I'm fully awake. At this point I usually give up and fall asleep normally. Where am I going wrong?