Brightness on Dell xps 13 not working!

Hi when I try to use my brightness keys for my screen on my laptop the indicator appears showing the brightness go up or down but the brightness is not actually changing. I am able to fix this by just restarting my laptop but it keeps happening whenever I use my laptop for a bit. It's a pain in the neck to keep on restarting my laptop to fix this issue! Anyone got any ideas how to fix?
Thanks,

Peter