system works 100% when continuously being used (using firefox for web access) If left for relatively short period of time mouse movement becomes intermittent and does nothing but move the pointer. Need to switch off power to reboot then system does what its supposed to do.
Hi @omhie ,
Welcome to manjaro 
Please try to open a console window and run htop. Then leave the system idle and see if there are any processes running which consume a lot of cpu / memory / io.
just done this . what do I look for? Have a rolling screen of info but no idea what that tells me.
Run htop and click on CPU% to sort by CPU usage and then when system becomes unresponsive make a screenshot of it (or a picture) and post it here. 
You can do the same with memory (MEM%) too