I inherited a Samsung CRT SyncMaster model #750s manufactured in 2003,

I don't have a computer handy, to check if it works, but I did plug the mains wire in to the wall and the screen saver 'box' came on indicating ;"check signal cable". Seems okay, nice colour but every several seconds it momentarily (fraction of a second) flashes, as if refreshing itself. Is this normal? All else seems normal.