2005 ford escape xlt awd v6, vehicle "jerks" as it accelerates from 0 to about 40mph. First few "jerks" are hard then then get a little smoother, until 40 mph is reached. When slowing down and then resuming speed, it jerks again.

SOURCE: SPEEDOMETER

I believe that would be the VSS or vehicle speed sensor.. Its located on the rear axle.. I would get the part directly from a ford dealer as the one I got from an auto parts store did not work correctly.. It cost about 33 dollars from ford and It is an easy change for a do it yourself person.. Kip

SOURCE: shakes at 60 mphexplorer xlt

Tires would be the 1st place to check. If you seem to feel it more in your legs then it is likely the front, if felt more in seat bottom then could be a rear tire. Depending on how severe the vibration is there could be a tire developing a tread seperation and should be checked right away. A simple balance of the tire and wheel assemblies may be all that required also but when on a balancer they should be able to tell if the tire has a more severe problem.
Driveline components could cause vibrations also however if the above sounds like it fits then check that 1st.

SOURCE: my car is jerking while accelerating and reaching certain RPM

I would look for a fault in the ignition system such as a cracked spark plug. Might need a scope check to put your finger on the problem

SOURCE: my car is jerking while accelerating and reaching certain RPM

clean mass air flow sensor check for mil light

SOURCE: 2005 ford escape 3.0l AWD XLT - DRIVESHAFT CARRIER

if there is some one in your area that balances driveshafts they can change just the bearing for you