Jumping over lava sets you on fire

Not always, but when you jump over lava it can set you on fire. In a parkour course there was lava below and sometimes I would set on fire when jumping over it. I know I havent fallen in and I'm lagging because I set on fire and then it comes off- I am also still on the block. I continue but it is repeatedly doing it and it is random. I am about 3/4 blocks above the lava when it happens. I am sorry if I cant answer all of the questions on this I am only 11.