One of the belts in the tire could have and torn you may not be able to see it from just looking at it until it bulges or blows out. This happened to me and it got worse as I drove faster. I thought my front end was out of alignment but it wasn't.
Your tires may be out of balance - look on the inside and outside of your rim to see if there is any evidence of a balance weight which may have come off. You would feel this but it would likely not be severe. I see them all the time in street gutters. You may have front end problems as most minivans have solid rear axles so not much to adjust there.
There are so many suspension parts in different types of cars now it's hard to say what little part might be the culprit.
Clearly the best thing to do is go to a tire shop and have the tires checked first. Then you can go from there. i buy all my tires at Costco so it doesn't cost anything to have them check them. You probably have a tire warranty so use it.