Car doesnt rev up occasionally

I have a 2009 nissan sunny automatic.  Around an year
back while i was driving the car all off a sudden it lost the
acceleration.  The car just kept on rolling.  I parked and
switched off for a minute and when i restarted it was reving
up and later until a month back every thing was ok.  Last
month same issues developed of non rev up and no
acceleration,  but everything goes back to normal after a
switch off and restart.  I replaced the plugs and for 2 weeks  
there was no issues.  But since yesterday the problems
arouse again and the instance of occurence had increased.  
Sometime i have to restart engine 8-9 nine times o find the
acceleration.  Even i am losing the acceleration while on
the move as well.  Please advise.. I am tensed.