Volvo: 2003 S60 stuck in park, shift lock, intermittent problem

Question
I have an intermittent problem that I can't get my car out of park.  I've found that if I overfill the transmission oil just a bit, after a few minutes, it moves out of park.  It's taking me longer and longer to get it out of park when it happens.  Does getting the transmission oil changed fix the problem?  What do you think is the problem?

Answer
Manuel,
I bet the problem is the shift lock. That is an electrical solenoid that only allows the shifting out of park when you step on the brake. Start the car and step on the brake now try to shift it. If it still locks up all the time have a tech check out the car, demonstrate the problem.