here have a tap on the shoulder
'I just want the motivation I once had back.' feelsbadman, unless you have something to aim at, you cant be self-motivated for shit
you are the only one who can act in order to reach this, trust yourself, you will not regain the once-lost things so better to stop craving for them, search new joys, maybe a hobby? girlfriend? God? name it and make it:)
personally,i tried working until exhaustion, partying, womanising, alcohol, substances, all fucking false friends...
good luck man, cut yourself some slack
p.s.: i know you have an important position to fill in your workplace, but check out the cheapest tickets, pack a backpack and travel somewhere so you can be alone with yourself and think, meet new people, see amazing things, a change of environment might sound bullshit, but its proven to work
also, maslow-pyramid, what level are you at?