2005 NPR. Trans works fine for 3-5 minutes then slips like there is very low trans fluid and won't move. After a few minutes it will move a short distance again. Ideas? Thanks

 

First check fluid level - if ok then Take clear bottle drain little bit fluid, watch and smell it - if dark, burnt and muddy - internal clutch worn or water intrusion into filling neck - then probably you need transmissions rebuild. Also what's transmission service light on dash illuminate - orange or red