So adrenal cortex weakness does not seem to be the cause, assuming you were not especially amped up on the day of your saliva test.
Do you have symptoms of catecholamine Depression and inattentive ADD. That would likely be related to the adrenal medulla.
When that is the problem I'd expect the person to be able to have enough physical and mental energy to do the things he likes to do but not so much to do boring tasks.
You could also investigate low thyroid but I would not settle for just a TSH test. I'd want to include Free T3, maybe more.
Eventually you could look at mitochondria support.