To answer your questions:
a) what does x 是 x mean? Here the verb1 + 是 + verb1 is a common pattern used to emphasize the verb or to build up to the next part of the sentence.
b) what does it mean in this context? In this context it can be translated to "(what I am) afraid/scared is being afraid/scared of these pain/suffering without a reason/cause"
c) what are other similar examples using this structure? You can basically use this pattern on any verb, such as
A: 气什么? What are you angry about?
B: 气是气在你的无知! Angry, I am angry about your naivety/ignorance!
A: 等什么? What are you waiting for?
B: 等是等你准备好! Waiting is waiting for you to get ready!