Best answer as chosen by user monica 211: Try This
Go to www.malwarebytes.org and download their free(not the pro version which costs) scanner and run a full system scan. A virus usually causes the problem you are describing and Norton may have missed finding it. Don't panic that Norton might have missed something. That can happen as no single anti-virus product works 100% of the time. Let malwarebytes scan and when it finishes it will show if it found anything. Just select the remove all found objects and reboot your computer. If nothing is found by malwarebytes then hopefully someone else on this site can offer better advice. Wish you well.