A change of autobox fluid usually makes a big difference. If you are a competent DIYer, take the sump pan off, clean the very fine filter and remove any swarf/debris from the magnetic blocks in the pan. However, you will not be able to change all the fluid as some will remain in the torque converter. The colour of the existing fluid will give an indication of it's condition, ie, brown instead of crimson indicates the need for a change.
Your symptoms might indicate that the autobox internal pump may be starved on it's suction side, hence the need for a filter clean and fresh oil