Delayed shifting into 4th when cold

[Ken92SVX]

I have noticed that occasionally I have a problem that the transmission does not shift from 3rd into 4th (drive) when it is cold out (around 20 degrees Fahrenheit or below); it stays in 3rd with rpm about 3,000 rpm at 55-60 miles per hour. Letting of the gas does not cause it to shift either like in normally does. It just stays in 3rd and eventually shifts after a mile or so of being in third.
This happens in the first mile or two only. Once it shifts for the first time into 4th then it does not have a problem again when starting out thereafter.

Is this normal or does it signal an impending tranny problem?

Thanks in advance for any responses.

Ken