Question PC slow start when cold boot.

Feb 13, 2020
I bought this PC second-hand and use since then about 3 years already , but lately it start acting weirdly . If i turn it off after using and start it right after that , it would start normaly. But if i turn it off overnight or like 2-3 hours the next time i turn it on , sometime it would boot immediately , some time it would take like 3-5 sec to boot or sometime the led on , fan on for 1 sec then off , i have to press power button again and wait like 3-5 sec to boot normally .
When it booted , it work normally , no crash , no blue screen ... . At first i thought it was power button starting wear out , but seem not like that , i just need to press the button 1 time and it will start eventually , but this annoying me and worry pc gonna fail one day.

My spec :
Window 10 1909 ( lastest update ) , 16gb
Mainboard H87 pro4 ver 1.80z
CPU 4771
VGA GTX 1070
PSU Seasonic Focus Gold 650w
System run on a SSD

I have turned off Fast Start-up in Window.
Reinserted both RAM but still the issue.
Gonna update the Bios but according to this site , but seem like mine is a beta Bios version and ''Improve i5, i7 non-K CPU performance'' so i'm not sure it's safe to update ?