Win10 throttling internet speed after awhile?

[thetokezen]

Hey guys,
I have 1gbps download and 100mbps upload. Everyday without fail after awhile (i think it's after leaving PC idle but can't confirm 100% yet) my download will cap out at 5-6mbps and only if I restart my PC will it go back to 1gbps. I thought it might be issue with the router (I'm using Orange Funbox 3.0 as a modem which goes into xr500 router and then to pc using cat6 ethernet cable) however no other PC on the network is experiencing this issue.
I am at a loss here, any ideas?

 

[thetokezen]

Forgot to mention my PC hardware in case it's relevant to the issue:
Motherboard: X99s
CPU: i7-5930k @ 3.5Ghz (no OC)
RAM: 32gb @ 2400mhz CL16
GPU: GTX980 4gb (no OC)

Let me know if I can provide anything else that might help troubleshooting