iPhone hot - battery dropping fast - low RAM despite no apps open

Hi,

I have a 4S running on iOS 7.0.4. The iPhone sometimes gets extremely hot and I can practically watch its battery power drain. I noticed that AWAYS when this happens, free RAM is low (typically below 20 MB), so it could be some page treshing bug in iOS of kind.

I say bug in iOS because this happens even if I do not have any third party apps open (mostly use iBooks, Email and Calendar). And yes, background app refresh is off, as is iCloud and Siri.

I can temporarily fix the problem using the "Battery" utility to detect RAM memory usage, I use it to reallocate memory when its low. The Battery utility typically will free memory towards 150 to 220 MB. Once that's done, the battery drain stops and the iPhone starts cooling down.

The frustrating thing is that in the background - even when I do nothing but use iBooks - free RAM steadily will go down in a matter of minutes! The cycle starts over: RAM usage goes up and once it falls below 20 MB, the iPhone will get hot, I notice, re-allocate memory, iPhone cools down, etc etc.

My questions:

1. Is there any App or iOS setting which outomatically frees unused RAM memory (without me manually runnung the "Battery" utility)?

2, Where can I see which App or system process eats up the free memory?

Many thanks,

HJ