In most cases it is not a lack of willpower but rather an exhaustion of the same. Try do arrange your daily routine around things you WANT to do and limit the things that burn attention and mental energy (doom-scrolling social media, ….).
It’s all about managing your (dopamine) resources economically.
I make workout my me time: my music, my time, my body.
Viewing working out as something that is good for me instead of a chore also does help. Concentrating on my body, really feeling the muscles contract is kind of a meditation to me.