Problem Gpu

[kishorekis]

Hi guys i have been owning a asus rog tytan g30ab and i was able to play all the games at a decent frame and suddenly while i was playing gta5 on pc My pc started to lag...Then i restarted my pc...Then everything was fine when i bought witcher 3 and started to play using geforce experience reccommeded settings At first few minitues everything goes great at 60fps then suddenly my games starts to lag and takes some time to load every frame and when i quit the game and restart the game it still lags when i begin the game not even the first few minitue....Then when i restart my pc and play the game it goes great for a few minitues and starts to lag after a few minitues......Every single time i had to restart my computer to play the games without lag..Please help guys...My pc specs are 

 

 

1]cpu-i7 4770k

 

2]gpu-gtx770

 

3]ram-8gb 1800mhz

 

4]motherboard-intel z97