To me, 'bound to' and 'likely to' refer to probabilities, where 'bound to' is much more certain.
'Prone to' refers to a natural aptitude, (or in this case) inaptitude. A common usage is 'accident prone'. I would use it with 'feeling' rather than 'feel'. It suggests that the person is naturally nervous. Liable is similar, but has a meaning something like 'likely to suffer the consequences'. As John said, 'liable' and 'prone' definitely have negative connotations, which the first two don't.
'Apt' is not commonly used in that sense - sufficiently so that I can't be sure how it is normally used. It is much more commonly used to mean 'appropriate'.
As John said, likely to and bound to both work in that sentence. Which one to use would depend on how likely you think it is that he would be nervous. 'Prone to' would work in the more general statement "He is prone to feeling nervous..."