I can sympathise so
I have low-level depression to (have had for as long as i can remember) which occasionally gets very bad. Motivation can be a big big issue.
When i see that i am getting into a rut, or possibly sinking into a low patch, i desperatly try and do somthing about it.
First, and one of the big things that helps is good food and pleanty of water. As much fresh fruit and veg as i can get and lighter meals things that feel and are full of goodness and energy. I avoid anythng that can be classed as comfort food.
For motivation i set myself goals. things like 'This week i will do 10 minutes of yoga every day' just small things and aparantly nothing to do with what i actually need to get done, but doing somthing and somthing small and easy just gives me a kickstart.
I also do two things which seem to contradict each other.
Firstly i set an alarm to make sure i am getting up and moving at a good time everyday and not stying in bed being lazy. I need to get into a routine of doing things.
Secondly i try and break up whatever routines i have so that i am not stuck in a rut. If i find that recently have been watching the same TV program everyday i will make sure that i do not have the TV on at that time. Even if i am not being productive, just doing somthing else reminds me that i dont have to be doing that at this time of day and the world will not end if instead i spend the time doing somthing (else which can be productive.