You better be very short if you expect to sleep in your car that way. Do your best to have a cargo van or other vehicle that allow some room… more room than a regular car allows. At a minimum I recommend a long-wheel-base pick-up with a camper shell.
If a car is all you have then let’s get some advice on how to deal with that if you are forced to sleep within it. This video covers only the most basic sleeping aspect. There are many more aspects if you actually live in your car. There is advice elsewhere in this blog and on the Web covering the many aspects of vehicle living.