There are quite a few YouTube tutorials on how to convert your car to sleep in it- not sure of your budget/where you hike but here in CO by far the most popular vehicle for this is the Subaru Outback. If you remove the back seats you can sleep completely flat so you don't have to sleep at an angle, and it has decent clearance + AWD for dispersed camping. Other hatchbacks might offer similar specs too. Have fun!
If you want to get super comfortable, check out tutorials like this one where you can add storage and a livable space to the back: https://youtu.be/7PTwJCW84bs