My car wobbles at high speed?

So I have a 2000 Ford Explorer XLT and it has about 147,000 miles on it so by no means is it a new car. The thing is when I go about 55 and above on the highway, it starts to wobble quite a bit. Now I have like 3 different tires in it so not sure if that is the reason lol but I'm not sure if it's something with suspension or not but it really concerns me when I drive to and from school. A lot of people say the cause could be tires but considering how old my car is, I'm starting to think it's the suspension components.

Take it to a mechanic. One time I had a wobble and mechanic found a weak spot on one tire that would bubble out at high speeds. He said I was lucky I didn't get a blowout.

Sounds like your wheels need balancing.

Spend some money and put a new set of tires and get them all balanced.

"Now I have like 3 different tires in it".

Yup, that would be an obvious culprit, Alex. That and/or they are simply out of balance. When is the last time you have had all four wheels/tire balanced? It's worth the tiny bit of cash needed to do so if you want to eliminate the wobble.

You have three different tires?

No no no no NO. Do not do that.

A steering wobble indicates either a wheel is out of true (buckled) or a wheel alignment is required. I would bet on the latter. The three different tyres is not necessarily an issue if they are similar types and wear, though you may want to put the matched pair on the front. Worn suspension doesn't usually result in wobbles on the highway. You generally feel/hear it when you're cornering or riding bumps. You can quickly check the dampers for oil leaks by eye. They will have fresh oil visible or a whole load of dirt stuck to them if they've been leaking a while. Dampers/springs do wear and fade over time and you can swap them out if you want, but I don't think they're the problem.

With a Ford Explorer it is important that all your tires are the same size. But i'm guessing the problem is with your wheel balancing. Get all 4 wheels balanced

You need your wheels and tires balances

Tires that need balancing can cause that very thing.

Have your wheel balance checked and your alignment checked. You can't put two different size
tires on the same axel. As long as you have the same size tire on each end of the axel it's ok.
have your shocks and struts checked.