Quick hardware troubleshooting question.
 

System hangs intermittently at all stages of boot (initial boot screen freezes for 2 mins with no system activity, then it starts to boot at normal speed again for 20-30 seconds, then freezes on the next screen for 1-2 mins, then fast again for 30 seconds, etc). It happens both before and after the OS loads. Any ideas on what hardware components would most likely cause this type of behavior? Thx!