Here is a pretty good answer: http://www.trustmymechanic.com/htmlmessage8.html
The car is out of alignment.
Not necessarily, but it should be checked anyway. The front wheels on your car are referenced off the back 'trailing' axle so if the rear axle was off then the entire alignment is off. Older vehicles and many pickups are referenced off the ' driving' or 'fixed' rear axle but the rear axle is non-ajustable where as your cars is. This is a more precise way of alignment.
Tell me the year and mode.
Yes
When you take your hands off the steering wheel with the car moving and it goes to the left or right quickly.
A tire alignment is not necessary when changing tire sizes. You can tell by the wear on your previous tires if you need an alignment. If you have uneven wear, get an alignment.
usually there is a button or switch depending on make of car that can turn it off ( not totally advisable ) read the cars manual and it will tell you where it is
$10 Off Wheel Alignment
Take it to an alignment shop.
If always in the same car, it's probably a wheel alignment issue. If in different cars, the person is a poor and unconcentrated driver.
There are a few possible causes, but probably the most common is wheel alignment and/or balance.
Before-a bad alignment cannot "unbalance" a wheel, but an unbalanced wheel, if bad enough, can throw off an alignment.