Notebook Boot and Lockup

I have an HP ProBook 6545b notebook computer with Windows 10 Professional 32 bit installed. (It came from being Windows 7 Professional).

The computer started up and I signed in with no problems but about ½ hour later I looked and the screen was dark but the hard drive light and the power light were both on.

I shut it down and almost every time since this occurrence, when I start it, the time screen will come on for a split second and go off, the plain lock screen will come on and go off back to the dark blank screen.

If I press the enter key, the sign in screen will come on with the box to enter my password but immediately goes back off.

Once in a while, when first turning it on, just for a second, I’ll get the Windows logo with the circular dots but it goes right back off.

I’ve tried pressing the “escape” key at first boot, to get the HP “F” keys to bring up diagnostic operations, but to no avail.

I’m not sure if it might be the HDD or the RAM or maybe something else.
Now, the computer is about 7 years old so I’m expecting that something may have or is in the process of failing.

Any ideas?