I saw this movie when I was a kid early 80's (the movie could've been much older as we barely had access to any TV shows where I grew up) and made me like sci-fi movies ever since. It takes place in space, a spaceships stops to investigate why a bunch of ships are clustered together in the middle of space. There was this tentacled monster with no face that travelled from one ship to another and killing the crew by grabbing them with the huge tentacles, putting them in its mouth and then spitting out an incinerated body. There was no escape as the monster seemed to move directly to the next ship. I'm dying to see it again, gave me nightmares at that time but still a good fantasy.
That sounds like the "Dragon's Domain" episode of Space: 1999.
Pilot Tony Cellini on Moonbase Alpha, which is traveling the galaxy on Earth's wayward moon, is beset by memories of an earlier deep-space mission of which he was the only survivor. His vessel came upon a cluster of derelict alien spaceships and docked with one; while they're exploring it, a swirl of lights fills the main corridor and a one-eyed tentacle monster materializes. It grabs crewmembers and stuffs them into its maw, then spits out dessicated corpses. It uses some sort of mesmerizing ability to persuade its targets to give up resisting. Cellini escaped in the command section of his ship, but there was no evidence of the monster and he was accused of abandoning his crew. Cellini abruptly begins suffering nightmares and visions of the same swirling lights in Alpha...
Full script and related information at http://catacombs.space1999.net/main/tscript/z23dd.html