I have tons of experience with this. Both in my current Jeep and before in a 1986 Chevy Blazer I had. In the Blazer it ended up being a tire balancing issue. I had 39.5 Swampers on it and they just wore wrong. As they get older, they change. I found that rotating the tires helped for a while, but the problem did come back after time. Are your tires radial, or bias ply? Radials will stand up much better, but you usually can't get them in bigger sizes or pay big bucks if you do.

With my Jeep it was a combination of a slightly bent tie rod and track bar issue. The first thing you need to do is go through the whole front end. Make sure everything is tight, nothings rubbing and you can't see any obvious problems. A front end component could be damaged by either normal wear and tear, or a recent fourwheeling incident. Just go back and look at everything and try and remember if you banged on anything during a run.

My guess in your situation would be tire wear. I saw you posted that you were looking for new tires. That probably means you have just hit that point where the tires are just gonna be fussy until you replace them.

I will finish by saying I feel your pain. The "death wobble" is probably the scaryist thing i have ever experienced in a automobile. The first time it happened to me, I nearly crapped my pants and sat o the side of the road for quite a while to compose myself. Do some research on the net and you will learn tons about it. Good luck