1) Simple phobia 
fear of being buried alive
(taf″ә-fo´be-ә) irrational fear of being buried alive.
Taphephobia: Fear of being buried alive. A phobia is an unreasonable sort of fear that can cause avoidance and panic. Phobias are a relatively common type of anxiety disorder. Phobias can be treated with cognitive behavioral therapy using exposure and fear reduction techniques. In many cases, anti-anxiety or anti-depressant medication proves helpfu...
Taphephobia is the fear of being buried alive.
[n] - a morbid fear of being buried alive
taphephobia, taphiphobia, taphophobia 1. A fear of being around or near cemeteries. 2 In psychiatry, an abnormal fear of being buried (alive).
noun a morbid fear of being buried alive