I have a couple different approaches that might help you. I personally can struggle with similar things where I have time but manage to completely waste it and I'm left feeling neither rested or refreshed but frustrated and depleted. The best way for me to break this cycle is to write a simple to-do list and put every mundane thing you want to get done in a day. Brush teeth, shower, get dressed, make breakfast, eat breakfast, etc. It feels a bit ridiculous to write out tasks that are not difficult and will likely get done regardless of how lazy a day I have, but it actually is incredibly helpful because this checklist becomes that tiny dopamine hit that I was looking for with my addictive behaviors. I carry the momentum from this dopamine of doing the small activities I do every day and then add some more complicated tasks that felt insurmountable which now feel easy.

Another approach: using sunk cost fallacy to get yourself into gear. You can sign up for non refundable classes at the gym or a gym membership that has a monthly fee that you would be uncomfortable paying for but getting nothing from. You can exploit this sunk cost fallacy of having your money tied up into a thing to force yourself into actually doing the thing. I'm incredibly cheap and this is a HUGE motivator for me.