Hi all!
After an update (at least I suspect) I rebooted my osmc and the splash screen graphics was glitchy.
After the boot screen is loaded I hear an audio noise (clicking and screeching) and screen goes blank (or starts turning on and off automatically).
I tried formatting a new sdcard from scratch, same problem.
After some tried I understood that only forcing in config.txt the system to boot in 720p is making it work.
I really have no clues of what could be…
Thanks for your kind time and patience 
Try change the HDMI cable.
You are a legend!
I used another hdmi cable I had around and it works like a champ!
This cable does not allow me to use remote control of my samsung tv to control osmc.
I will go tomorrow and buy a new one to fix all the issue 
Which kind of cable will allow me to use the remote?
Thanks really a lot, fantastic help.
You need a cable that supports CEC (like 2M HDMI cable - OSMC).
CEC works via 1-wire bus (Pin 13 on the HDMI cable). Most cables will tell you if they are CEC ready or not. Assume if they do not mention it, that they are not. You want an HDMI 1.3a cable or later (which adds audio functionality for CEC)
Sam