Hi Steve,
The fear of having a panic attack certainly can trigger a panic attack in itself. The theory goes that its the day you truly believe you cant have a panic attack, is the day you wont have one. By accepting and embracing the fear, you can avoid panic attacks. Panic attacks is a type of fear that its based off fear, so it feeds itself..so the fear of having a panic attack certainly does make it more likely to trigger one.
Certain situations can invoke a panic attack too though. Its typically a situation where the person thinks they cant 'get away' in some form. Its a blockage buildup in my opinion that's constantly being diverted by the person, that eventually breaks through in the form of a panic attack that lasts a few seconds. The reason it usually hits when the person feels they cant get away, is that they feel they can no longer continue to block and protect themselves and then the fear sets in and everything falls apart just for a moment.