Why my wifi in my android phone stopped by itself?

[AC Question]

I have an htc desire 816g phone and i bought it just couple a days ,every time i leave my phone with wifi turned on for a while then i returned to use it i found the internet and all the applications is not connected while the wifi signal is full, so i have to switch the wifi off then on again to work properly.
so is it normal or i have something defect in my phone?

 

[Rukbat]

Settings/Connections/WiFi. Press the menu button. Advanced. Keep wifi on during sleep. Set it to Always.