Won't start

Symptoms: turn key - hear a click, electrical comes on, but nothing else happens. Had the starter replaced a month ago. This happens periodically. Also, when I press on the brake, I hear a clicking sound in the shifter. The last time it wouldn't start (3 days ago) I hit th shifter a few times and it started. It seems like the shifter is a bit loose, if I hit it a few times, it starts. Any clues? I am at the point of selling it since no one can fix it. Thanks!

it is a 94 nissan sentra gxe auto 70K miles with all scheduled maintenance done.