metro.co.uk/2013/06/15/sold...
Standing for long periods of time can be common a trigger for a syncopal episode. If you have to stand still, then clench and unclench your calves or rock forward on the balls of your feet to encourage blood flow.
For further advice, see Dr Wieling’s film where he demonstrates useful counterpressure manoeuvres illustrating the direct effect they can have on blood pressure. stars.org.uk/patient-info/t...
Pre-syncope symptoms for up to a week at a time
Diagnosed with vasa vagal syncope 
Sudden slow pulse with POTS?
First time fainting.
