Version of Java and SQL Developer?
Which Look and Feel are you running (set in first page of Preferences) ?
How about a screenshot of how it looks when it opens?
I've not seen an issue described such as yours before, but I'm sure we can figure something out.
When you say your screen turns on and off, do you mean your physical monitor, or a 'screen' in SQL Developer like a SQL Worksheet?
OS - Windows 10 64-bit
java version "1.8.0_201"
Java(TM) SE Runtime Environment (build 1.8.0_201-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.201-b26, mixed mode)
SQL Developer version: sqldeveloper-188.8.131.52.1748-x64
What I meant screen turn off or on, I mean the laptop screen. I do not see an option to attach file. I will send email with the attachment.