I recently purchased a used Volvo GL Wagon 4cly automatic. It is such a sweet little car, and I love to drive it. I usually drive Corvettes, so in the performance category this Volvo is night and day. But here is the problem. I drove it for about two days with no problems then on the third day it began to refuse to upshift properly or shift out of 1st or low gear after sitting idle and not running for a period of time. I noticed that if I accelerate until it seems like it is going to blow up, or at least until it hits 45mph in low gear it will eventually shift from low to 2nd and on up, after the initial "unsticking", the transmission works flawlessly until I once again park it and wait for at least 30 minutes or more. Then it simply refuses to shift out of low gear. I have tried manually shifting and it still will not upshift. Normal upshifts seem to come at 20mph (there is no tach). I wish I could figure out what I have done, because it was running great and then just suddenly seems to refuse to upshift unless I really get down on it. I don't mind taking it in for a service check, but I am pretty much the type of person who would like to know a little bit about what's going on before I turn my cars over to a qualified mechanic. Can you shed any light on this mystery. Why will it shift fine after unsticking, but not shift at all after sitting and not running overnight or more than 30 minutes? I can find no noses or cables off or out of place.