My 2002 Chevrolet Prizm rides smooth until it hits 60-75 mph. At that point it starts to vibrate, getting worse the higher it gets until it passes 75mph when it smooths out again. What could be the problem? Alignment? Balance? Something else?
Alignment? Balance? Something else?
In short, yes - alignment, balance or something else would pretty much cover it.
There are a lot of things that can cause this. It would help if you included more info about the condition/history of the car. E.g. how many miles are on it? How old are the tires? When was the last time it was aligned? Any other work done lately? Have you asked anyone to look at it? If so, what was done/said? Etc.
The first thing I would do is just have the tires balanced and rotated. I would have this done by a reputable mechanic, and ask them to give everything a once over to look for problems that may cause this.