iPhone 6 Freezes and Restarts.

Hello! I will like to inquire how to trouble shoot my iPhone 6s+. Since the last iOS 14.2 update, I have been having issues with my phone freezing suddenly and restarting, I could be using apps like Safari, What’s app and YouTube and it suddenly freezes, blacks out and when I resume the app it takes me some steps back to either the home page. Or sometimes at 89% the phone suddenly dies and restarts. The phone capacity is about 128G and I don’t use more than 64G to avoid pressure. It’s been happening frequently about 5-6 times daily (for the last 4days) unlike before when it happens just once or twice a week. Thank you.