Idk, all of that also feels a bit like being in a coffin for some, especially if you're going reasonably far into the tube. I do get the sleepiness bit, though personally would prefer it cooler.
Ask to be cooler - the airflow can be increased and depending on how compliant the tech is, the heating (SAR) can be reduced. A slightly longer, but cooler scan.
Every scanner I’ve ever seen has an option for a mirror to see out, so that may be an option. Most magnets from the last 5 years are about 1.8m long, which helps. Some research magnets or older ones are a fair bit longer.
Not saying I’m normal, but I really like sleeping in tight dark spaces. A couple times I’ve thought of building/buying a coffin-like thing specifically for sleeping in. The aversion is totally reasonable, just trying to say — for some people the coffin-ness is not a drawback