does it happen any one gear the most or just all? Try This, with the car stopped engine running shift from first to reverse with a ten count hold in neutral. If it cluncks into grear or will not go into grear at all. These may be needed to be looked at If this continues, look at the clutch hydraulics, maybe it needs seals and or fluid change, or even air/waterin is in the lines
Happen to mine I changed the fluid and all was fixed