May sound silly, but you should take some measurements and see what you find out. You stated you drive in an 2018 Ford F-150 all day at work and no issues. Then you get into your RAM and most likely the difference of the pedals/positioning of feet/seat etc may be different enough to cause agitation. A bigger difference/example would be going from stick shift/pedal all day and then regular automatic. The difference in where your feet are placed/spaced/located/touching/resting could be factors.
Does the F150 have bucket seats too?
Ergonomically designed for the masses gets changed up quickly when given the ability to "adjust" everything from the seat/up/down/angled etc... to the pedals "adjustements" to the resting of opposite leg factors. Feet resting vs feet dangling can bring on tingling sensations of "body part going to sleep" type scenarios.
I would set up my RAM as close as possible to the measurements of the F150 (seat and pedals) as close as you can and see how that works out for a couple of weeks.
The Jarhead(ya know that is a compliment coming from an old Army dawg

) Srminosky brought up excellent point about the wallet and sciatica issues!!! Could be the newer seat of the RAM repositions your wallet differently than the used seat of the F150 thus shifting your wallet to cause issues.
I don't know if you "literally" driver most of the day or just in and out of vehicle etc... if your not feeling all day and then suddenly feeling it in the RAM, sounds like adjustment issues. Like if you keep your head tilted at the wrong angle for hours sleeping and then waking up and trying to straighten it up/you get that feeling of the body saying ohhh noooo you had me positioned like a triangle so here is some pain for wanting to straighten me up now kinda thing. <----I am going through this now...lmao!!!
Another weird scenario is new shoes---don't laugh---coming from the Safety side of work we issued new fitted Redwing steel toe boots to 60+ people for safety purposes at manufacturing company. The "learning curve" those employees went through with the many different aches pains discomforts...to oh these feel great. Turned out many of them had been used to wearing sneakers/old worn boots/etc...leg/foot muscles/boots too heavy had to adjust to a quality boot. After few weeks "everyone" loved them once their body and minds adjusted (except 2--had to custom fit order--then they were good).
Just a few thoughts!!!