You could try to fake it until you make it so to speak.

Accept that your motivation is low now and just go through the motions of doing something just for the sake of it.

Keep doing it, stick with it using your intellect until one of two things happens: you finally finish what your started or you find a glimmer of motivation. Either way you win.

If you finish what your started that's a win because you accomplished something even though you weren't motivated.

If you find a glimmer of motivation that's also a win because it means you've found a way to recover at least a little motivation and might be able to find more if you keep going.

I've been depressed for years now and use this same technique. I haven't found motivation yet but I'm accomplishing things and hoping I'll find motivation some day.