3.0 tdi occasional hard to start

Hi folks

Engine is hard to start sometimes, however no consistencies to it, has only done it about 4 times in 8 months, when try to start engine starter motor could turn for maybe 10 seconds before starting, despite always waiting for all lights to go out before starting, immediate restart after it happens, thinking glow plug but should it either have a light on, or happen more often / be getting worse? What's the average life span on your experience of glow plugs on these engines? I read somewhere that they stay on for a while to help the engine run better? I don't mind doing the plugs and probably will just thought it strange it's not happening more often under same conditions, has anything similar happen anyone?

Thanks

CCW engine by the way

Thanks Karl, I have had it on a snapon machine and no codes, I'm buying vagcom myself soon, I'll probably do the plugs if one is gone others probably not far and not too expensive

Mine had 80k on it when I bought it so if yours is anything to go by then there due