SMDH at these kinds of posts.

OP how the hell do you expect us to have any suggestions for you with the limited information you posted. Please be more thorough explaining what the car's doing, what work if any has been done to it recently, when did your problem start, how many miles are on the car or put on after any work was done to it, are any warning/SES lights lit up on the dash when you try to start it, etc.

 

 

So I'm just guessing since you provided almost no details but here's what I think is happening.

-You CLUTCH was slipping (flywheel doesn't slip, the clutch does).

-You took the car to Nissan for a new clutch and possible a new flywheel.

-Nissan replaced the components

-Now the car won't start.

Now if Nissan did take the flywheel off then they probably didn't put it on correctly, there is an alignment pin that MUST be lined up on the flywheel for the engine to start, ask them if they bothered to check the flywheel alignment pin. Refer them to section EM page 149 under cylinder block assembly for pictures and directions on how to PROPERLY install the flywheel.

 

Basically the flywheel can physically be installed in ANY orientation but only one way is the right way and if they didn't get it installed correctly then the engine will not start, or it will start and run terrible.

 

Also that section and page is from the Factory Service Manual.

 

If you don't post more specific details I'll close your thread. It's just taking up space on the forum as is.