VW Beetle 2001 - Weird nose + crazy shifting

A big hello to all of those nice people here, I hope any of you have a clue of what is going on here. I have Volkswagen New Beetle 2001, 2.0L gasoline engine. It is standard, and It is having some weird shifting problems. Again, this car has an automatic transmission, but it seems to be that when the engine is warmed up sometimes it will not shift to the 3rd shift, it will only stay on the 2nd, and it will do it with any shifts from 1st to 2nd or from 2nd to 3rd. Also, when this happens it makes a little noise like those noises that wet belts in the engine make. Does anyone has a clue of what this could be? thanks so much for help you can provide.

Do you have any warning lights on when this is happening?

Yes, I have the engine light on, but I had it on before this problem, and volkswagen technicians told me the light was on because a O2 sensor was broken.

If you don't have an OBD-II scanner, I would take it to Autozone for a free check. They will tell you what the codes are and what they mean for free. It is possible that you have more than just the O2 sensor code if your transmission is giving you grief. On a side note, get the O2 sensor fixed. You are probably getting terrible gas mileage, and if you are not, you will be soon.

Ok, Im gonna take the car to auto-zone and see what the code is, thanks!

This is gonna sound weird, but only an oil change fixed my problem.