What happens between you sitting down in front of the computer and you beginning to add words to your work?
I suppose a part of my difficulty is tied to lack of motivation, but a big part of it is not really knowing what to do next after I’ve opened up my text again.

Scan back through. Reading what’s already happened resets my brain, up to a point. If the break is day to day, I only go back a chapter, but for longer breaks, I’ll go all the way back
I looked into what well-known authors do and I believe it was Stephen King who said something similar. There’s also someone that recommended you append a couple line summary of what you wrote at the end of each day. The next day, you can simply read that to get going again.
Oh that sounds like great advice
Same, I’ll read through the last bit, make some edits as I see things, then pick up where I left off. Also: OP try to park on a hill where you can - leave off where you know what you want to do next so it’s not as hard to get going. Best of luck!