CPU running hot, no idea why - Throwing CPU over temp error

• CPU - i7-6700k no OC
• MOBO - ASUS z170-e
• Cooler - Corsair H100i
• Monitoring software - Speedfan

As the title states, my CPU is running hot. I get the "CPU over temp" error when I start my machine occasionally after it has been off for hours.

I have updated to the newest bios, I have tried to set the voltage to 1.3v, turned off the turbo boost in the bios, reseated my cooler (H100i v2) with new thermal paste (yesterday.) After I reapplied new thermal paste the temps dropped from 50c while gaming to 40c, and idling at 35-40c to 28-32c after.

Here are the details on the temps:

Start up it runs at ~75c while idling. Gaming it doesn't go up much maybe a degree or two. This is only sometimes though, I will restart a few times then it is ok and back to reasonable temps.

I am not sure what else to try, I've tried everything I can think of. Any suggestions?

Edit: Formatting