If this problem continues, I would look to see if there any other programs running in the background that can be turned off. Is this something new, if so what was the last software that was added? Does it seem to happen at startup more often? If so it could be background process doing their auto updates. It could also be related to your antivirus program and it’s scheduled scans and updates. Without doing the CTRL+ALT+DEL and seeing what app has the largest percentage of CPU time we can only make a few suggestions.