Question weird issue pc auto restart

[awayagain]

Hey everyone i posted days ago about a power supply issue (wich at the end was'nt it was my motherboard ) link :

https://forums.tomshardware.com/threads/what-power-supply-to-choose.3730976

After Installing the asrock b460m steel legend everything is fine my pc turn on since first start everything is fine

but now only three days when i put an external hard drive pc shutdown and restarts auto

played ryse son of rome after two and a half hour gaming my pc turned off also and restarted

tried occt and aida for 10min test stress nothing happend

 

[awayagain]

UPDATE :
now after 2-3min of aida64 stress test cpu or gpu
pc shuts down for a two three sec then starts again by itself

 

[awayagain]

anyone ?
update 3 : my pc shutdown after plugging anything keyboard mice then after 1-3sec start again by own