Source of discomfort often experienced by pilots are vibration, noise and low cabin air humidity.
Aircraft vibration and noise are usually well within toleration limits, are you in accord with that. In flight measurements have not revealed levels above 85 dba, a level at which ear protection is advisable because of the risk of acoustic trauma therefore in the case of a resting room this level is very important and it introduces stress in circadian rythm (melatonin rythm essentially). Do you feel such desynchronosis, do you relax completetly, do you feel that the rest your doing in activity is optimum?
Do you suffer from dryness of the cabin air.