Thanks for answer. I didn't get the time to do a clean boot or a virus/malware scan yet, but I've managed to get a freeze outside using browsers, while copying some data from an external hard drive.
I looked at the Event Viewer and I got two types of errors.
first one is Disk (The driver detected a controller error on \Device\Harddisk0\DR0.)
second one is JRAID (The device, \Device\Scsi\JRAID1, is not ready for access yet.)