Hesitating trouble with my car...

[Badinfo]

Hey everyone! alright, here is yet another problem that has popped up with my 1992 300E. Sometimes when I press the pedal all the way dowon (not past the switch), my car will shift, but will just ride along as if it were in the higher gear for about 5-10 seconds, then it will suddenly start to accelerate like it should. It is not shifting during this time, because the shifts on my car are firm (I call them harsh) and noticiable, and I don't notice any more shifting. Sometimes the car will just not accelerate at all, prompting me to let of the throttle and mash again or just cope with a car that would get 0-60 in about a minute... Also, just as randomly, the car will run just fine. Any ideas as to what might be the problem?