why paranormal experiences are scary?

I'd say it depends on the experience. But generally anything considered paranormal is outside of our current understanding, and anything that's outside of our understanding is scary just in itself.

Why? Because our human brains cannot grasp the concept of life after death, or demonic beings preying upon us at one given time.

None. Because they're not real. Takes all the pressure off once you realize that.

Our senses have limited capability. To realise something exists out of that capacity and cannot be understood, is sort of scary.

I had some pretty scary ones myself in the past.

well, whatever the cause, when reality starts misbehaving it's intense as fuck

Lack of control, people fear that which they do not understand

All ?!