Are you sure your tires are balanced? A balancing weight may have popped off somewhere. I've had DW on two separate occasions and both were tire related and not drivetrain related. The first time I somehow knocked off my front tire weight which caused wobble at about 65-70ish mph. Not terrible but bad enough to cause alarm.
The second time was when my tires got so bald they could no longer balance them (I was young, just had a baby, and broke and couldn't shell out the $1200 for new tires at the time). After a while of driving them like this, they got so bad out of balance that from about 50-65 the shaking was so bad I was terrified that the Jeep would just rip itself apart. I could literally feel the front tires jumping off the ground. The weird part was that if I mashed the skinny pedal and burned through that window to 65mph or so, the shaking could be avoided...but if I had to slow down past 65mph...god help me lol.
Long and short, in my area tire balancing is free or really cheap and only takes about 30mins. Wouldn't hurt to have it checked out.