You will need to take your vehicle to the dealership or an ASE certified transmission shop to have this problem diagnosed. The transmission uses solenoids to shift the gears and there is a 3 to 4 shift solenoid, there may be a problem with it.
Another possiblity could be that a valve in the transmission is stuck or not working properly and that's why you feel the hesitation. The worst case senario is that you would have to have the transmission replaced because the problem could not be fixed. This is why you need a good diagnosis.
To find an ASE certified shop hear you, go here:
〉 Answered on Feb 27th, 2007 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines