car shakes, speed reduce on it on and car completely cut off. on 2007 Chrysler 300

Outstanding Vehicle, in which I had since 2007 (now 2010); servicing and upkeep has been maintain; recently while driving the car started shaking and then even though I was on the gas, the car gradually slowed down. After pulling over on the highway shoulder, the car preceded to shake even more before cutting off completely what could this be

Asked by for the 2007 Chrysler 300
I have red the question of yours car, I am having the same problem, while driving on gas and also gasoline, when I am driving normaly on one speed it starts to shake, when I take off the speed it stops to shake or when I make my car drive faster it also stops to shake..
I am havin this problem for more than a year I guess, my car is made on 2004 december.
So the reason why am I writing - is to ask you - have you got trough the problem and maybe you can help me to solve my car by saying what was wrongg on your car..
also mechanics cant say whats the problem - they just cant find it - the car is in absolutely good condition.
I have drived to chrysler centre (in Latvia, thats the country where I live) and they said that I need to change cardan (I hope you do understand the meaning), so I changed it - and nothing changes..
Waiting to hear from you some kind of info, please dont hestitate to reply.

evuxx2 at gmail dot com