After screen timeout, blinking screen+8 second delay before the screen comes back up

[AC Question]

So I got a galaxy s6 edge w a cracked screen (cosmetic only, touchscreen works fine) from a friend for a reasonable price- $125. But when I start it up after the screen has been off for a while, there is an 8 second delay. This is shortened if I try turning it back on right after the screen times out- if its within 30 seconds or so, its only a 1 or 2 second delay, but if I haven't hit prepped it in a while- say 5 minutes or so, then the screen just blinks 8 times (1x each half second or second)- the blink is just a horizontal white line about 3/4 of the way up the screen. I have tried changing up the settings and have even done a factory reset and this is still an issue. Can anyone help me at least figure out what the problem is, and fix it?