2000 SLK 230 Acceleration

I'm considering buying a nice little 2000 Mercedes SLK 230 (two seat hardtop convertible).   Everything seems okay on it, but when I go to stomp on it to check the acceleration, it only slowly accelerates - it does not downshift to increase the rpm's and give it that jump like it should.  The gears seem to shift fine with the manual automatic, it's just when I'm driving in automatic.  I'm hoping it may be a solenoid of some type, but want to present that question to the group.  Any insight would be helpful - thanks!

 

John in Vegas