Hi Paul, my name is ***** ***** welcome to JustAnswer!
Does this issue seem to always happen after you have signed into the machine?
Hi Paul. My name is***** you for your question and the opportunity to assist. See if you can get to a stable desktop starting the machine this way:
Start or restart the machine and as you see the computer manufacturer's logo on the screen start steadily
tapping the F8 key at the top of your keyboard. You should be brought to a startup menu.
Using your arrow keys select Safe Mode and press enter.
When you get to the password ***** log in and see if the desktop comes up.