Here is what I know about myself...
A lot of it for me, is emotional at times. If I am looking forward to the activity or event, it is like I am caffeinated with energy. If it is something I am dreading or am not really amped about, I seem to get tired and bored pretty quick. Not saying that is you or anyone else, but just an observation.
Physically, it does/can take some time to get into a groove, adapt to new stimuli and make it a habit to do regular W/O's, see results and keep pushing.
Getting motivated can be a pretty big deal by yourself too, and if you have a partner, coach, trainer or crew you could W/O with, that could be a plus.
As far as supplements or specifics on what to do/use, I am probably not an authority, but I know you can build up stamina and energy just like you can build up a muscle. So do not despair.