djunikoscratch

Hey guys i have a Clk 500 2005 having a problem with this error code P0778 but its wierd because sometimes the car works normal like shifs good and everything but other times it shiftshocks at startup and doesnt shift after first gear! im reading up on the error code but it says the pressure solenoid B is bad but other sites tell me my transmission fluid is low or dirty can someone help me to save some money on spending 4000$ on new tranny or just change the oil for 300$ do u guys know if when a transmission is bad it just gives up or does it act up sometimes like its doing it to me because it might be dirty or low? thanks!