Transmission Problems???

Hi everyone! I have a 1997 VW Jetta and lately it's been jerking when shifting from one gear to another, and also when pushing the gas after having pushed the breaks. Yesterday it just stopped while I was waiting at a light, and this morning it was stuck in first gear. It would not accelerate although I was pushing the gas. Is it a transmission problem? If yes, does anyone have any ideas on how to fix it? Please help!!!! I appreciate any suggestions.

Thank you!