Imac wont start up

[Gbroer]

Hello,

Since about 1 week my mac wont start up. Sometimes it does, but most of the time it doesnt.
It gives me this screen (attachment) at startup. After that the screen will just go blank. I tried alt-command-R-P but no luck..
Anyone knows the solution?
The problem started out of nowhere.

Thanks

 

[CoastalOR]

Looks like a video problem. See this recent thread with a link to Apple support page:
https://forums.macrumors.com/threads/vertical-bars-on-display-hardware-problem.1967585/