Chrissmiles

I am having intermittent problems for the past year in which after I drive for 30 minutes or more and I get to my destination, once I return to my car to start it, it does not start, and takes me anywhere from 5 mins to 25 minutes before it starts again. I have not experienced this problem in the morning or if I should drive to a destination and then it's hours before I start my car again. So it seems that it's happening after I've driven awhile.
So far I've been hearing it's my NSS (neutral safety switch)? But another mechanic told me it could be a problem with my cylinder's, he said I should get a Leak Down Test.
Can anyone tell me if they've experienced this problem, or suggest solutions base on this intermittent issue.
Thank you
Chris smiles