Is it legal to take a nap in your vehicle in a parking lot?

For context, I work strictly nights 5 days a week. Sometimes ( like right now as I’m about to clock out) I just have a very hard time trying to stay awake. I have a few times in the past pulled over into a Walmart or restaurant or gas station parking to to doze for about 20 minutes just to make my commute home safely. I’ve heard conflicting answers as to if it is ok to take a short nap. Any help would be greatly appreciated