I just came back from my first solo car camping trip at Valley of Fire State Park!

I chose this park because it's only a short 1 hour drive from Vegas airport. Valley of Fire has seasonal closures starting May, so I was lucky I did the trip in April! It's pretty hot during the afternoon, but nights and mornings were pretty temperate. It doesn’t usually rain.
There's cell signal at some parts of the park, and paid wifi at the visitors' center. There’s also really only one road through the park so I wasn’t worried about getting lost, and the road leads to all the attractions.
I booked ahead of time via Southwest and picked Fox because it was the cheapest. Turns out it's kinda far away from all the other car rental places and took 2 shuttles to get there instead of 1.
Booked a campsite on the website ahead of time! The camping fee includes entry to the park and is pretty good at ~$20. I got into the park late at night, and just drove in because no one was at the gate.
I picked a compact SUV so I know I can flip the back seats down, and lie flat in the back of the car. It would've been comfier with a mattress pad but just sleeping bag and using a jacket as a pillow worked well! I just turned the car off and cracked open one of the front windows by ~1 inch.