Hello Alex,   I would try removing all PCI devices from the server, then powering it on. If you don't see any change in behavior, then you'll want to take it to the minimum to POST and try again. If the server POSTs without issue, then you can start reinstalling components to see what has been giving you an issue.   If you have iDRAC access, you may be able to login in and find this information provided.
I found the following error on one Server Power Edge 320, how can i solve it? Thank Alessandro
Problem on Server DELL 320 power edge