What could this be? vibrating/fluttering feeling @r external iliac/femoral artery, sometimes followed by a feeling like a warm saline flush

Blood flow: If you have not had recent trauma, surgical interventions, indwelling lines at the area you are describing you should be fine. However at times some patients develop a small leakage from their vessels after trauma, surgical interventions, and/or indwelling lines that some patients describe as painful and that is accompanied by vibration, if this is the case you should see your doctor.