Your body may just be adjusting to the new flow of magnesium available ....
waking up so to speak.

When I use magnesium, I have much reduced leg cramping, and muscle tension. I don't get much of any twitching, however.

My main twitching may occur on long fasts as required by testing needed at the doctor's. I've a left lower leg achilles/calf muscle area that twitches like mad if I am very hungry or have low blood sugars. I even got to show her that one...she was impressed. But I haven't had it in a while now since using the magnesium lotion.

One day, is not really a useful time frame for supplements. So if the twitching stays for weeks, then I would be more concerned.
Supplements typically are pretty slow to act.