My laptop will not turn off properly?

i have an acer aspire laptop. for a good couple of months it hasnt been turning of properly (by clicking start then clicking shut down) when i do this it will say shutting down with the swirly sign but will stay on that page and wont do anything else. the only way i can turn it of is by holding down the power on, but i know that doing that is bad. what can i do?