Slow loading and black screens

Just got all our furniture etc out of three months storage and on starting the pc the screen goes black after signing in for 2-3 minutes before the desktop loads and also goes black again for several minutes when opening any app. Managed to update windows to latest version. Ran SFC and DISM and it reported several issues fixed but still the same. Was going to try fresh install but could this be hardware related? Checked everything is seated correctly etc. Thanks for any advice

Things to do:

1) Check RAM for errors, One app is MemTest:

2) Check hard disk health with CrystalDiskInfo or Hard Disk Sentinel:

3) Search for System Restore and load it. This is a tool that stores restore points (much like checkpoints) so if anything goes wrong you can restore your system to an earlier restore point that was in better working condition. Check if there are any restore points to go back to. If there are more than one, try restoring to the previous from last point as usually the last one might not complete successfully or might not solve your issue.

4) As a last resort before doing a new installation, download the Windows 11 ISO and try to do an upgrade to the same or newer version. Even if it is the same version, doing an in-place upgrade/repair will fix any system file or configuration errors and you might avoid a format and new installation. Since Windows 11 25H2 was released a few days ago, it is a good opportunity to both upgrade to 25H2 and repair your system. Two in one! Scroll down to the third option to download the ISO directly:

If anything else fails, then I'm afraid you must backup your data, wipe the disk and reinstall Windows 11 (aka do a clean installation). Again, you don't have to install the previous version, just download the new ISO and install Windows 11 25H2 directly.

Thanks will try these tests or reinstall as necessary