2006 nissan extended crank

First start in morning you can hear fuel pump run. After driving short distance such as Wal-Mart 8 to 10 miles. Shut engine off. Come back outside and start engine key has to be turned on an off several times before engine starts. Sometimes when starts engine stumbles an misses for5 to 10 sec and then smoths out . Car has been doing this since about 40,000 mile and now has 65,000 and getting worse. What do i do . Thanks Phil