I agree. You are using stock cooler, right? It will not be able to deal with so much voltage, drop it to 1,35V, for temperatures over 65C set the fan to run at max, and then see what overclock you can get. Extra fans in the case would also help to keep temperatures down (Ryzen stays stable better at lower temperatures).
My R5 1600 heats up to ~75C at 3775MHz, 1.36V, PRime95, and I'm not willing to OC more, as voltage requirement, and heat output jumps up right after that.