I'd start with pregnenolone, the grandmother of the steroid adrenal cortex hormones. note dhea is not abbreviated.
http://en.wikipedia.org/wiki/File:Steroidogenesis.svg

Notice preg is the immediate precursor to prog. It is otc and dirt cheap. You might start with 10mg x2 or 3/day.

Preg + GABA/glutamine have been almost a magic combo for a close female friend with decades of PTSD.

adrenal support, including a little dhea, preg, glandular, etc affects many hormones so the effect on well being is subtle and varied. However I feel younger and more vibrant even in middle age. I don't get as much of a mid afternoon lull, etc.

Be aware of the sfx of taking too much. They are not pleasant. I had some of that briefly when I did not tolerate the doses of dhea my doctor had suggested. fortunately I had done my homework and knew the sfx.

After saying all of that, I'd bet your problem with lack of motivation is more on the adrenal medulla side, not the cortex side of the adrenals.

That is where noradrenaline and adrenaline/.epinephrine are made.

Look up catecholamine Depression and inattentive ADD.

This is much more complex to support with supplements as I can attest. I've certainly gotten nice gains from them but they've been hard and complex to tweak. Inattentive ADD / cat dep are by far my biggest remaining problems. A couple years of Cutler protocol heavy metal detox plus related supplements did wonders for my long list of symptoms that had messed up my life for decades.

You are fortunate to have the Internet for digging for clues : ) I had to rely on clueless doctors. for example
//www.curezone.org/forums/fm.asp?i=1951581