2002 Nissan Sentra Please help!

Hi there!

I don't know anything about cars, I had this car since 2002, I had a major tune up last year in Feb spend almost $3000 on it, All of a sudden it just stop power went off, I turn off the ignation and try to turn back on, it work fine, It works fine when it is on the freeway, it just stop at the stop lights.

Not sure what seems to be the problem


Thank

Kiran