I've driven nude many times, some places where it wasn't illegal, some places where it was, often for hours at a time in daytime. I've even gotten out and pumped gas at a self-serve gas station late at night, (I did put on a wide brimmed hat because there were surveillance cameras above.) I've always had a pair of shorts next to me which I could quickly lay across my lap.
I've had two or three occasions where I actually had to talk with a police officer, only once where it was illegal. I was pulling out of a parking lot at a national park area in Canada just after dark, when a Mountie pulled in. I put my shorts over my lap. He got out and talked to me through my window, because no one is allowed in these parking lots after dark. He checked my license, and was shining his flashlight around in the car, and did ask me if I was naked. I said no, and he said, OK, he just wanted to confirm that. I'm not aware what the penalty for being nude would have been, but he didn't pursue that any further. But, if he'd asked me to step out of the car, I think I'd have been in trouble. As it was he just let me go with a warning about leaving those parking areas before dark.
You have to use some common sense, like not driving where there are bigger vehicles with drivers looking down into your vehicle. Especially, if you're a guy, or have male anatomy. There was a guy who was on an interstate highway, I believe in New Hampshire, driving an SUV with his pants down, in the middle of the day. A larger truck passed him on the left, and the driver saw him, thought he was masturbating, and called police. The guy was pulled over, and charged with various things, and it was all over the news. Now, I doubt this would have been quite the same had it been an attractive female naked from the waist down, or fully naked, even if she was clearly masturbating. Probably the police wouldn't have been called by that truck driver, but then again, another female driver might have called police. Definitely, not worth the risk.