For what it's worth, this was on a Reddit thread, which really surprised me, since I have taken magnesium glycinate (I now take magnesium threonate). In case it has any relevance for you...
"Magnesium glycinate is Mg and glycine. Not just magnesium. Yes magnesium has weak antagonism for NMDA, but in some people L-glycine can have an agonist effect at certain NMDA receptor sites that can increase wakefulness/make them agitated/excitatory"