This may not be the answer you’re looking for, but we advise against sleeping in your vehicle while it is running. In unique circumstances, your exhaust system can malfunction and lead to a buildup of carbon monoxide. While this rarely occurs, that is still a risk that it might happen.
This suggestion is referencing sleeping and parking outdoors, but we want to remind you to never let your vehicle run idle in an enclosed space for longer than necessary.
It’s better to just accommodate your car to sleep with the engine off. This can be done by bringing extra blankets or cracking the windows—depending on the weather.