2000 Volkswagen Jetta Loosing Power

I was driving 65 mph on the highway & all seemed good. Then it started to loose power.
I pulled over & turned it off for a few min.
It started bk up but would only go 4-5 mph. At the most. I parked the car over night & called for a ride. The following afternoon I got in the car & it started right up & ran fine.
I just purchased this car last month from a private party & I cant afford to dump much more into it. And scared to drive it again & get stranded in the middle of no where.
I'm confused as to what it could be that's wrong with it.
Can You Help me Please?