I had been having nothing but problems with my S5 since the Lollipop upgrade a few weeks ago. Then, less than a week ago, I saw your recommendation to try uninstalling Facebook and Facebook Messenger. I was not using the Messenger so I only had to uninstall Facebook. That definitely did the trick. For the past week, since uninstalling Facebook, I have not had any significant issues. I think it's now running at least as good as it was before Lollipop. Thank you.
My wife has an S5 also, she has Facebook and messenger with Lollipop and hers runs fine...mine is JUNK!
My battery life went to pots since Lollipop. I have been putting up with it for months now hoping an update fix would come out. This was after repeated useless calls to Verizon. The only good part is, they sent me a new battery. It's not any better, but I do have a spare now.
It's always good to check the Apps permissions.. it show whats being used and whats not.. I like the App System Panel it shows the Apps running and what the CPU is doing the temperature of the CPU and Battery.. this app has done Quite well for me the 5 years I have used it..
System Panel App.. in the Google PlayStore..