speed restricted

[ArtR]

I have a 2004 Maxima SE. This problem has occurred three times now with a week or so between each occurrence. While driving, the car will slow down to about 25 mph and will go no faster - it does not stop running - it just won't speed up. If I stop and turn off the ignition and wait for about 5 minutes, when restarted it runs fine. The car has 95k miles and this is its first real problem. Any suggestions?? Thanks in advance for the help!

Art