Internet connection

I just switched to COMCAST XFINITY, Why am I having so many issues with connecting and stayind connected to XFINTY Wi Fi?  Everytime I put my MacBook Air on stanby,  I have to log off internt in order to reconnect.  There has been times I have to do this twice and sometimes I HAVE to restart my lap top in order to connect.   Is there something I need to change in my preference.  I have my own Motorolla routet/modem combo brand new so that's not the problem.

Thanks

ER Duffy