Sometimes the pressure about having to do it can mentally stop you emptying your bladder. Also not everyone has the need to go and pee in first thing in the morning. It doesnt sound very often when it happens 3 in the past few months, but if it becomes more frequent then have a word with the doctors. It could well be psychological and your 'brain' is stopping you pee as you are thinking about it too much and you are tensing your muscles stopping the flow.
ps im not a nurse so if anyone else is a nurse that works in that field please jump in, but I do work for a urology supplier.