Why is my car dying while its in drive

2003 nissan sentra GXE. While im driving on the highway my car dies, it seems to die after i have drove 20 miles at highway speeds and after the 20 miles it usually dies I get over a hill and start going down a hill the RPMS just drop to zero and all my gauges turn on and i pull over and try to start it and it wont start up right away it usually takes 5 minutes to start. I will continue to drive home and it will die in 2-5 miles instead of the 20. My car has 148000 miles. My car has an automatic transmission.