I recently decided that i wanted to finish the blood and wine dlc after not playing it for a while. for the past few days the game was running pretty much perfectly without any problems. however, when i tried to play the game today, it just would not start. there are no error messages, no log appears for crashes, i have tried various fixes posted by other users online but nothing seems to work.
when i open witcher 3, the game does appear on the task manager but disappears after about 3-4 seconds. any help would be appreciated

here are my specs:
intel core-i5 3570k processor
Nvidia gtx 770
8gb ram
Windows 10

Your very first step should be a simple reboot.

tried that several times

I have exactly the same problem. Yesterday the game played fine today it has the behaviour you describe. Tried to force window mode through registry or delete the saved files but nothing changed. I am really confused.

If you're playing the game through Galaxy, verify/repair your installation. Also check your security software. Sometimes an antivirus will update and flag a program as a false positive and prevent execution. Disable it for troubleshooting.

tried that just now, still not working

Then uninstall / reinstall. Your saved games will be safe, provided you tell the uninstaller to keep them.

tried uninstalling / reinstalling, still not starting

Did you update your nvidia drivers yesterday? Eventually that was my problem, I rolled back and now everything is fine.

no, i actually only updated my drivers today after the game did not start

If you have taken all of the suggested steps, then without doubt something on your system is causing this. Since nobody but you knows your system, diagnosis on-line is all but impossible. You need to troubleshoot your own system to determine what is preventing the game from starting.

yes i just decided to reset my system to see if that would change anything and now the game seems to work. However, now i get a different problem, from time to time when im playing the game the screen just goes black (game is still working) and it goes back to normal when i press esc. any idea what might be causing this?

Sounds like either a driver (graphics) or hardware (GPU) anomaly, and likely to do with Windows 10 and your low RAM (8GB is low).

wow, i actually just realised what the problem was lol. because i reset my pc i didnt realise that screensavers were turned back on which was making my screen black if i didnt touch my mouse and keyboard for 5 mins (im so stupid)

Ah, easily done. Thanks for the feedback.