Clutch sticks?

More often than not, when I shift to 3rd gear, even if the engine winds down for a couple seconds or so, the 3rd gear seems to grind in to place even if the clutch is pressed in all the way, and I am curious to know if there is any do it your self diagnostic or clutch lubricant of some kind. Any advice or trouble shooting tips to see if it's just me doing something wrong would be very much appreciated. thank you

What car is it?