Terminally slow laptop

Hi,
I upgraded my Sony laptop last week from W7 to W10
i3 processor, and 4gb RAM - 500gb HDD.

At first, it was fine,and booted up very quickly.

Recently it isn't....:(

Typical times:
2.5 minutes to log in screen
3.5 to desktop
4.5 minutes until all icons are showing
5 minutes until browser opens

On shutdown, I have set the PC to hibernate if I shut the lid, but the fan still is running 5 minutes later, but if I reopen the lid, the PC never responds. (Blank screen, whirring fan) for over 30 minutes.
Now the only way to shut down is press and hold the power button.

Clearly something is wrong.
I have checked start up items:
Avast, and malware bytes only things starting apart from the touchpad, and a couple of Intel things.

I probably (definitely) need to go drastic here.
Last night I did a macrium backup image.
I have several as well as a rescue usb
1. Before loading windows 10
2. Immediately after I loaded windows 10
3. One I did last night.

I have the DVD from the media creation, and usb files which allow the PC to boot from rufus created sub. (Tested ok)

My feelings are that I need to scrub absolutely everything.

1. Do I try a reset from within windows 10?
2. Is it recovery?
3. Is there an option to go back and remove programs etc?
4. Should I reformat the HDD, and load windows 10 from the DVD?
5. Should I try and restore to "just after upgrading to w10" maccrium restore?

I have no real preferences, but want a faster laptop no matter what it takes.

Thanks

Terminally slow laptop