Can't open file manager after 24 hr continuous use of Ubuntu 16.04

Question

If I use my Ubuntu system for more than 24 hrs, the file manager closes automatically. And if I try to open it again, it opens and closes immediately.

I tried to open it using the command sudo nautilus, but that returns

Maximum number of clients reached
** (nautilus:31308): WARNING **: Could not open X display
Maximum number of clients reached
(nautilus:31308): GnomeDesktop-WARNING **: Unable to open display ':0' 
when setting background pixmap

Segmentation fault (core dumped)