Normally, mine would be around 3am, because everything is quiet & I'm unlikely to be disturbed/hassled by anyone - however, the quiet sometimes allows the anxiety to notch up - in which case sleep is a fine place to be... Unless the anxiety finds it way into my dreams, in which case... Well, you get the idea...

Basically, it's whenever I can feel relaxed, or can get my head wrapped around some task that'll make it feel engaged. Or eating something with enough cholesterol to knock over an elephant...