hesitation

I have a 98 Beetle that is having some issues. When I start the car, about half the time it won't start on the first try. I have to press the gas pedal while I turn the key to get it to start. I am also having issues where it hesitates upon pressing the gas. I actually almost got in a wreck...

When the car warms up and I step on the brake, the car jerks to a stop. Same thing when I give it gas. It lurches forward. Once it starts moving it's fine. The check engine light is on. I used gas filter cleaner in my tank but it didn't help. Any suggestions?:confused:

Changed the pre-cat O2 sensor a week ago. No hesitation since! This has been bothering me for years!