Shifter/shifting seems to be become stiffer/less smooth

Hi guys, quick question.I've been riding my bike now for 2 years but I'm noticing using the shifter needs more pressure than before with the left foot, it came gradually not instantly or anything. Is there any maintenance needed specific for the shifter? Oil levels are ok and chain tension/lubrication is too. There's a total of 38k km on my bike and it's from 1993. Honda Transalp. So not to much.I'm not a mechanic or anything but can do some checks etc. My self. Any tips are welcome.Thanks in advanceYke via /r/motorcycles https://www.reddit.com/r/motorcycles/comments/ep0f54/shiftershifting_seems_to_be_become_stifferless/?utm_source=ifttt