Default Always awake, car mode

Am posting this to get help for a friend who has the S5. He is finding his phone to be very hot about every other day with battery rapidly depleting. What could be doing that?

He has another issue where car mode launches when in his car, with bluetooth on, not in a dock cradle. What could be doing that?

My S4 hasn't done either of these, so I came here for help. He is stock/unrooted.

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Daily carry - Galaxy S4 (AT&T), ShoStock v8.1 (and jeboo) themed by JohnMcW
Busy time toy - Asus TF700, ZOMBI-X (Beta testing)
Media device for BT audio in the kitchen - HTC Inspire, Fallen
Media device for car audio - HTC Vivid, PAC-man 4.4 [AOSP]

You can't know your limits until you exceed them.

My other device is an all grain HomeBrew rig.