My xbox turns itself off a minute or so after it has been turned on

Out of nowhere my xbox froze so I turned it off by the plug then switched it back on. Soon to find out that after a minute or so my xbox would turn itself off. I have switched my power brick, dismantled my Xbox and cleaned the dust from the fan. Left it unplugged over night yet nothing seems to work. This problem occurred the day I got off back from my two week holiday. Also I am not sure if this may be relevant to the solution but my xbox does not display its content on my TV despite everything being fully operational. Any solutions would be perfect. Thank you