two possibilities: loose motor mounts or contaminated gasoline.
In addition, if you are saying it shakes going down the road at around 55 mph then you may have a tire out of balance, or a bent wheel.
might have misaligned or loose wheels
the cuase of this is ussaully worped rotars
Could be a problem with your torque converter
Cylinder miss, broken motor mount, or vacuum leak.
Cylinder misfire. Possibly failed or failing engine mounts.
The engine of the car may need to be cleaned or your oil may need to be changed.
Normally this is caused by a tire out of balance or a bent wheel.
have front suspension checked
Normally a bent wheel or tire out of balance.
i would really like to know myself
physics involved,to keep it simple roters. 65;
because the alignment is off Warped or out of round brake rotors/drums.