2006 Kia Sportage Please help.

Bought a 2006 kia sportage 4WD and the test drive was wonderful until we were headed home. Once the vehicle warmed up to normal temperature it began having trouble wanting to shift from1 - 3. It will run at high rpm in first then shifts hard once in second has problem the rpms will jump around and seems to have little or no pulling power. Now if I shift it manually it shifts fine and does not slip. Could it be the shift solenoid or an internal problem?