I have the same issue as above. Right before bed is typically suggested for bruxism, etc. Magnesium has also been shown in a study to improve sleep quality, though I don't remember the exact mechanism.

I might have an absorption issue though. Magnesium salt topical spray (less costly than pills) helps intantly unclench my neck/shoulders, and theres extant literature on that being an effective method of administration.

I don't take it on a schedule.

I only take it when I feel a twinge in my calf. I figure I'm probably deficient in magnesium or something. Even if it is a placebo, it seems to work.