Every woman is different but from my experience it starts with irregular periods then you have none for several months and then they come back again for a few months until they eventually stop and with me the hot flushes have started and in this current heat it is a nightmare. This usually starts around the 50 age group and can continue for several years - I am 53

Your periods have no schedule, they may become erratic. You may have a cycle and repeat only a few weeks later or not at all. Your menstrual flow becomes heavy, sometimes clotty. You have hot flashes where all of a sudden a wave of heat comes over you. You may have emotional out breaks for no reason, and you do not even understand why. This is most all of the symptoms I went through , it varies in intensity for everyone.