Mazda 6 S Transmission shifter not going into gear randomly?

mazda cx5
Hello I have an 04 mazda 6 s wagon with 5 speed manual transmission and i just started noticing this issue where ill be driving and every now and then its very difficult for the shifter to go into any gear, i really have to force it in. Sometimes it does grind, and I have to double clutch to make it a smooth shift. Its a bit random as sometimes it shifts smooth and fine. Anyone experience this? Not sure if this is a synchro issue or if I need to change my tranny fluid?