My iPhone wont start and can't even charge

I noticed that the battery was on 100% for a ver long unusual time, I thought it was something that would get fixed by restarting the phone. So, I restarted it and when I saw the battery it was at 16%. Since it was almost discharged, I connected it to the charger but it didn't charge anything, it got stuck on that 16%, it didn't charge but neither discharge, it would just stay the same. Then, when for some time I disconnected the phone, it went down to 9 then 6%, but if I left the charger connected, it wont discharge. To add to all of this, while it won't charge nor discharge, my iPhone kept restarting itself. I thought I left it connected to the charger overnight, but when I woke up it was all discharged and when I tried to plug it into the charger the only thing that it does is to keep flashing the Apple logo all over again (but only while connected) I really don't know what to do. I looked all over the internet for many solutions but none worked,

Thank You!! Yes it was a battery problem, I had to change it and already did and is working perfectly.