I decided today to take my SP4 as my primary rather than my old tablet. Put in in my car seat, set in sleep then hibernate, made sure it was facing toward the front so nothing would touch the power button. Was at 100% charge. 15 minutes later I heard the fan kick in, couldn't do anything about it in traffic. 45 minutes I arrived, it was down 75% and the pen magnet worked as a heat sink and was quite hot. Used task manager and found nothing unusual. Checked to see if Bluetooth had connected to my cars system, it was set to off and hadn't connected. Next looked at network and found "vehicle" listed under computers. Clicked it and it did nothing but open a blank window. I have a 2014 Equinox which doesn't use Microsoft for it Nav+ system. Leads me to think trying to link to at least one of my cars onboard computers is what caused the problem. Since a successful DSMI all my heat issues had resolved. Now I have a new one.