It may be getting too hot.
After a while the fans and heat sinks, and air outlets, get clogged with dust and dirt.
This can cause certain parts of the PC to run too hot and stop working.
Are you perhaps having building work done and there is lots of dust and dirt in the house ?
Take the PC case outdoors, remove the covers, blow out any dirt with a hair drier, carefully loosen any dirt or dust which is stuck to fans with something (not metal) like a small brush or lolly stick.
Make sure all dust has been blown out, and fans still work, put cover back on and try again.