Any pc restart loop,or on pc shutdown,the pc restarts,most causes are pc hardware conflicts..
Also,with the above being correct & its a laptop pc,chk youre pc battery charger,it might be faulty,or it might/must
be installed at all times,this being the pc battery is faulty.The faulty battery can still run pc if charger is installed 100%
of time,if this situation is correct,then plug in charger,wait 12-15 minutes before pc start.....