Have you run Malwarebytes free and run C Cleaner.
Make sure your anti-virus does not run a scan at start up set it to run at a different time..
Maybe to many programs running at start up.
And yes you could do with some more memory.
Have you any space left on your hard drive.
What security do you have including your Firewall.
A lot of laptops come with Norton pre-installed.
If so did you use the Norton removal tool to remove it.