I live in a northern city. It happens after I’ve been stopped, whether that be a stop sign or in the morning etc. Indicator lights says 4H but I’m actually in 2WD evidenced by my rear tires spinning. I’ve learned how to make it slip back into 4WD. What I do is I tap brakes to stop the rear tires spinning, then tap-tap on the gas and keep tapping gas until I feel that I’m in 4WD i.e. Truck goes ahead on ice without rear spinning so I know front axel is being propelled. It’s been going on all winter but I noticed it a couple times last winter. I learned that method by trial and error. I started by switching from 4Hi to 2wd and back and forth. Over time I learned what works. One casualty is my plastic switch cover cracked inside where it covers the switch toggle. I fixed that. So, here I am near the end of winter. Thanks for your comments and suggestions.