The moonwalkers of Apollo 14 were the first to sleep in the lunar module, although astronaut Ed Mitchell says it was hardly a restful night. NASA had decided that the astronauts would sleep in their spacesuits, removing only their helmets and gloves, so they wouldn't waste time or risk damaging the suits. But sleeping in the bulky suits was so uncomfortable that NASA subsequently changed the policy.
Mitchell also says the lunar module's perch gave him pause. "We were very concerned about the angle that the LM was on." We got up and looked out the window three or four times during the night, to make sure we were still upright and hadn't turned over."