I have the same problem(s) with my Tab 4 also, Model # SM-530-NU, welcome to the club! I went to 6 different repair shops (STAPLES, BEST BUY, OFFICE DEPOT, FRY'S AND MOBILE KANGAROO) all say the same thing we don't fix them just throw them away, unreal! Then they refurbish them and sell for $224.00 (U.S.), Samsung Customer service, after 2 hours on the phone, they wanted $296.00 up front and you send it to them and said it would cost $71.00 for battery replacement plus labor cost and $196 for motherboard, plus labor. Well I was fit to be tied, they could care less about their defective products after it was out of warranty(1 year). Always take out additional coverage on any electronic foreign made garbage today. Keep all your records on everything you buy today.
They have some good ideas on here, sometimes the battery connector (INSIDE UNIT) comes LOOSE and you have to open the unit. If your not handy, find some handsome guy to fix it for you. It's tricky, right tools and parts, a handsome nerd to fix it for you. When it come to reality, these so called techs(most) in these above stores don't know nothing about tablets (repairs) at all. Enough said!
NormG