I bought my 2002 Maxima GLE Auto in March this year and its had this problem since I got it, although I'm sure its got worse.
When stopped at traffic lights and the engine has reached running temperature the car jumps like its trying to change gear. Putting it in neutral stops it happening.
Also does a similar thing when increasing throttle on the freeway to accelerate or climb an incline, feels like its momentarily changing gear.
It would seem to be an electrical problem to me but I wonder if anyone else has experience of this problem and can advise.
I get a 'service engine soon' warning light from time to time but I'm not convinced this is related.
Also transmission fluid level is way over the dipstick level marks, but I wouldn't have expected that to cause this sort of problem.

 

Do your RPM's increase without the car reacting?

If that is the case then it can be either a slipping tranny or your MAF.

Go to Autozone / Advance Auto and find out what your codes are. Report back when you have em.

 

Vehicle speed sensor, its on the side of the transmission I had to replace it on my wifes I30t.

 

This sensor was not detected at autozone just so you know.

 

Thanks for the responses.
Been to Autozone today to get the codes read, they were:
Oxygen sensor: P1147, P0139 & P1167.
Brake switch malfunction: P1572

No speed sensor problem identified but that seems to be the sort of thing that would be wrong.

Any further thoughts.

 

Do the RPMs pick up without the car reacting?

It can sometimes give a bit of a jolt when setting off from rest but there isn't otherwise a problem with opening the throttle and the car not responding. Have I understood the question correctly?

 

i would try a new speed sensor first as well