Was just wondering if its normal for a phone to warm up during a phone call, during a call today that was 6 minutes roughly 7 minutes I noticed my phone was warmer, roughly 90 degrees according to thermometer. Also warms up using safari and facebook to about that same temp after 10 minutes of use. Happens on my X and my 7. Different Carriers, Different Carriers. Is this hand heat? or what? Not using a case. Trying to figure out if normal?