The shadows in your peripheral vision are moving again.
Not in a dramatic horror movie way but in that subtle shift-your-eyes-and-catch-nothing kind of dance. That prickle on the back of your neck shows up uninvited. The sense that something somewhere is paying way too much attention to your existence right now.
Scientists call it hypervigilance or maybe heightened spatial awareness when your brain goes into overdrive mode. Spiritual folks say you're tapping into dimensions beyond our normal perception. Your anxious friend swears it's definitely ghosts.