Start enable fuse 52 on c200cdi 07reg keeps blowing

[Amea]

Hi
I would appreciate advice about my C200cdi. A month ago it would not start. I checked the fuse and replaced fuse 52 with a 20 amp fuse. It has been fine since until it blew again. I have replaced the fuse and it's starting again without any issues. Any ideas on what's causing this?

 

[GAV105N]

Starter motor

 

[Amea]

Thanks. Should I replace the starter motor or wait till it blows again.