Reddit mentions of Nechkitter Windshield Wind Noise Reduction Foam for GoPro Hero 7 5 6 (2018) Camera Premium Shape Memory Sponge Reduce Wind Noise for Optimal Audio Recording Durable Anti-Scratch Protective Cover

Make sure you have the latest firmware update. Hypersmooth shuts off if the battery isn't delivery enough voltage (because it's too cold), but the previous firmware was a little agressive with this.

Regarding keeping the camera warm... it's not so much the camera as it is the battery. If the camera and battery are cold, then you stick the camera next to a hand warmer in your pocket, that doesn't do shit for the battery temperature, and nothing changes. Instead, consider keeping the battery in your inside pocket or anywhere warm, and then when your ready to use the camera, pop the warm battery in and go for it. The camera should generate some heat while running to help keep the battery warmer, and if you then throw it next to the hand warmer between runs, it'll do better.

That said, one way you can help retain the internal heat of the camera is to get a mic foam cover for it. It's usually meant to reduce the wind noise hitting the mics, but it also reduces the heat exchange with the external environment. It's like a little sweater for your camera. This way, if you KEEP it warm and have it running, it has a higher likelihood of staying warm with the heat it generates.

https://www.amazon.com/Nechkitter-Windshield-Reduction-Anti-Scratch-Protective/dp/B07LC5X28K/ref=pd_day0_hl_421_6/130-3766086-2861720?_encoding=UTF8&pd_rd_i=B07LC5X28K&pd_rd_r=7805987a-5691-11e9-a634-633eb631cbdf&pd_rd_w=X4zFI&pd_rd_wg=XyKxS&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=ZM5CECS8N1CRYWVR8Q5M&psc=1&refRID=ZM5CECS8N1CRYWVR8Q5M