Help on start up

Hi can anyone help, I'm a mac user but being of an older age know nothing about them. I have a Macbook air and recently updated to Sierra it seems fine except on start up where its doing something thats driving me mad. When I enter my password thats fine, but when it opens the desktop I get a pop up window asking me to enter login keychain password, which would be okay but there are window after window , as I triy to either cancel it or login, there is another window underneath, they vary from comm service, identityservice, cloudd, accountsd, if I did something to them all there would be 7 or 8. is there something I need to turn off or on , that I've not done right. As I say, I realy know nothing about my Mac other than I love using it, if there's something I need to do, please tell me in easy speak or I'm lost.