High rev after truck has been sitting for a while

[Ofz22]

I drive a company truck for work so my Ram sits in the garage and gets taken out maybe once a week. When I take it out and I’m pulling out of the drive way and start to get up to 25mph the RPMs jump up and stay there for a couple seconds then once the ole girl shifts it doesn’t do it again. The truck has been used once a week for the past two years and just cracked 100,000 miles and recently started doing this. Looking to see if anyone has some ideas what could be happening. Thanks.

 

[Jeepwalker]

Does the vehicle speed surge too? Does the transmission feel like it's slipping? Does it occur if you put your foot on the brake and run it through the gears (not moving) twice, after you start it in the AM but before you leave your driveway? Does your tk have a dipstick? If so, check the fluid level. If not, look under the truck for any transmission leakage or wetness. The first thing that comes to mind is fluid level.