Could be a problem with a tire(s) such as balance or tire belt separation. Also have the front end, steering and suspension checked for loose/worn parts.
I should have said that the car seems to sputter at those speeds rather than shake so I don't think it's a tire problem which most people tend to think of.
The van that is moving from 20 mph to 35 mph
90seconds
change your idler arm that should take care of it
The internal organs struck the inside of the body at 35 mph.
Sounds like wheel ballance.
35 feet at 30 mph requires about 0.8 seconds.
Check the wheel balance
its not spossed too...you may need to balance your tires
It would be highly unlikely.
3 meaters
Distance = Rate * Time or, for our purposes Time = Distance/Rate Time = 35 mile/35 mph = 1 hour