If it ''clicks'' as in the starter silinoid ''clicks'' then you're starter is more than likley going out.
I had a problem similar to this. Parked at Wal-Mart went inside got 4 things.came back outside....Click...click and it would not start...Towed it home...Took the starter out....Jumped it off by-passing the silinoid...worked fine...So i knew it was the silinoid...Went and got a new one but tested the old one when i got to the parts store...and it tested fine...
Got a new starter and have been fine since. What i'm saying is sometimes it's hard t diagnoise these things. But it is more than likley you're starter. That is if you're sure that the battery cables and grounds are ok.
