When I try to connect to wi-fi on my Samsung Galaxy S4 a message comes up, checking the quality of your internet connection and then network disabled because internet connection is slow. This happens at home and when out and about when other devices connect straight away. This has only been happening in the past 4 to 6 weeks.
First, please make the Question match your description (in description you wrote S3, in question S4).
To your question:
I think it can be disabled in WIFI menu. Press the Hardware "Menu" button, then go to settings.