MBP cannot start. Powers up hdd then shuts Down

Hello i was browsing the internet on my mbp (plugged to power) when it suddenly went dead. When i try to turn it on, it powers up for maybe 2-5 secs (ligth in the White led, hdd starts spinning) then shuts Down. It never makes it past Black screen to the Grey screen.

I have put ssd in the computer in the normal hdd spot and mounted hdd in the spare where dvd. Drive usualy sits, using an adapter. This has however been working flawless since april.

I have tried resetting smc by pressing L-shift + ctrl + option and power Button at the same time.

Cannot reset pram either.

Tried checking hdd and ssd connections to mb, as i had read that it could cause these symptoms.

Any advice on what i could try to do?