Default Weird problem with Wifi and Internet connection

Hi,

I have noticed that even when my Wifi is on it takes 10 to 15 second to my Note3 to connect to Internet ( till the two arrows are shown). For example starting Play store takes 10 to 15 seconds to connect to Internet. After that the connection is established I have a normal wifi speed.
BUT if I do a reboot I don't have this delay and have a " normal" connection time till it slows down again and till I do a reboot.

Any explanation ?

Thank you for help.

Daniel