Dodge Repair: my 2000 plymouth neon car shaking, plymouth neon, mechanical knowledge

Question
hi
i have Plymouth neon 2000 and recently it got overheated and i went to mechanic he fixed it and change the thermostat and coolant and he told me that i need to change the engine mount which i did and since then the car making noise and shaking every time i stopped i stop sign i can feel that shaking under my leg . i told the mechanic he sound like what wrong and told me give it sometimes because he just change the engine mount . another one says it is the breaks , third says that it is the catalytic converter fourth said that something is too tight that why it makes that noise and i got confused  and  i don't know what to do .
i can feel the shake once i turn on the car and also when you shift to reverse or drive specially when i stopped in stop sign
could you pleas let me know where is the problem exactly

Answer
sir  would u have any idea how to tell me how to fix something over the internet with out seeing it for yourself? If u tell me what part to replace then yeah I can look it up and give u the procedure other then that  i haft to go off what u say and with out having any mechanical knowledge and can tell me other then what u said  there is no way i can tell u what is wrong. Did the shaking take place b4 or after u had work done to it??  if it was after then would u not think it was something that was done  or not done?? If u over heated your car  maybe u burnt some valves or a head.