1 reads like general guidance for dealing with insomnia. If you only, for instance, sleep and have sex in your bed, then when you go to bed it'll tend to put your mind into those states. If you also read and do mentally stimulating things, then it'll be harder to relax the mind for sleep.

2 is sleep apnea.

3 is hypothyroidism (a common enough condition with symptoms of lethargy, apathy, depression among others).

4 I don't know.