Widows 8: Minecraft lags after 5-10 minutes?

Hi, my specs are…
Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
16 GB RAM
GeForce GTX 760

If you need any more, ask but here is what happens
I go onto my minecraft server, i can play for 5 mins sometimes 10 and then it just lags so much i don't even get 1fps. I have a good gaming pc, just bought it from overclockersUK, and whenever I try to put more memory to minecraft it just comes up with an error. Someone please help!

Nicholas

Hi, I have a similar problem but mine will just lag, does it so, will it come up with a crash report? But it might be your Wi-Fi provider because I play an A laptop and it work fine apart from usual lag.

Lewis