Wow, I thought it was unnatural to have no nightmares, seeing as I don’t have them either 
Well, there was this one somewhat scary moment when I was approaching a door with my friends and was really nervous about something in there, and then all of a sudden the door burst open and a wind-up toy jumped out and started rattling around on the floor. It wasn’t enough to wake me, but I felt my heart beat for that instant, and that was the only time I felt my heart jump in a dream. So basically, I don’t have nightmares enough to wake me up ^^ I’m arachnophobic, yet I dream about spiders sometimes too but they were never scary probably because they were quite hazy. In fact, I just had a dream this afternoon about some spiders I was trying to kill
It does make me curious as to whether it’s based on personalities, environments, lack of sleep (like me! 
) or something else. I have my own fears too, but I try not to let them get to me during the night. So maybe that’s why? I also never had many lucid dreams, and had practically no “natural” lucid dreams (meaning I never became lucid just by myself without the use of a technique)