As someone who recently went through a super long bout with unmotivation I can offer some possibly helpful advice, no promises made though. As Mikus stated, before you do anything you need to learn about yourself and your process. Are you most productive early in the morning, at night etc? I noticed I would get VERY lazy after lunch time. Here is my situation and how I kinda fixed it.

What I did to combat unmotivation was three things:

1. Get to bed earlier than normal.
2. Wake up earlier than normal.
3. Drink lots of coffee/tea and water.

I noticed that I was staying up super late to get "caught up" on work I felt like I should've done hours earlier. This was causing me to wake up later the next day, typically around lunchtime so it was just this feedback loop of demotivation and unneeded stress from missing deadlines. Also, waking up early gave me more hours before lunch, so even if I did hit a demotivational time; I had hours of work already done previously.

It was a couple of weeks of waking up early before I could really find a schedule and "settle" into work mode. It wasn't instantly a motivational bump. A few things helped, mainly setting up a routine and follow it to the second. Mine is typically, wake up - get coffee - shower - dress - sit down and email/reddit for 15 mins while I drink coffee/eat - check out my work tasks for the day and put everything into a To-Do app. I use Things.

Once I start work, I throw on Focus in "Hardcore" mode where I cannot turn it off even by restarting my computer so I am actually forced to do nothing BUT work. Also, spotify playlist are awesome, I use my own "Morning Productive Mix" but there are tons on Spotify.

I think demotivation comes from depression, for me at least. From this moment on, forward can be your only motion. Even if you're only doing one small thing a day, you're chipping away at stuff. No more zero days!

I'm not sure of your financial situation obviously but for me, it's all about putting bread on the table and the way I do that is from Design. I should be thankful I even have a position in the first place that allows me to be lazy sometimes. Of course, all this is easier said or erm..typed than actually putting anything into practice. It's going to take hard work to move past this time in your life but just remember humans are ever in flux and if you can be unmotivated, you can be motivated. Another added plus is that when you do work in a timely manner and you make deadlines that you follow through on, your clients or boss take notice. This will in turn make you feel better and will give you a bump of motivation and even possibly be making more money...maybe. Also, this might be a nice watch "Motivation is a Myth".

The hardest step is from 0 to 1 and it's what takes 99% of the effort.