[Help] What is going on with the car?

Need some insight. I have a 10 month old Shep/Pit/Gun dog mix. Her behavior in the truck (yukon XL SUV) has changed considerably in the last couple months and I don't fully understand so I'm not sure how to help her or if she needs something.In the past we'd get in the truck and she'd just lay down and sleep in back or look out the windows as we drove. Totally calm and relaxed. The last couple months have been different. I don't think it's fear but there is some sort of anxiousness going on.She doesn't avoid the truck, in fact I open up the back and she excitedly jumps in without me even saying anything. She isn't overly eager to get out. She doesn't whine, cry or tremble. She doesn't try to climb into the front with us, in fact she barely checks in with us at all. It doesn't seem to be any of the normal signs of fear you'd expect. What she does to is pace around, change positions (stand, sit, lay) and pants a lot. I wonder if its just be her being excited to be going somewhere but she doesn't act hyper either. It's just more like she can't get comfortable.We thought it might be something in the back of the truck so we moved her to the middle section. Same thing, she'll sit on the bench but then gets down, stands, sits, stands etc. She'll do this for the entire two hour ride to the camper.As far as I know she hasn't had any bad experiences. She's always had positive trips everywhere (she likes the vet), weekly dog park trips, going to softball with me, going to the camper, hanging with other friend's dogs, etcAnyone have any insight? Is it nervousness or excitement? Anything I can do help her out? via /r/dogs http://ift.tt/2rDS0bz