1. Running large programs or many programs at the same time
2. Having too many browser tabs open
3. Excessively running anti-virus and security programs
4. Not enough RAM or disk space
5. Installing too many unnecessary software applications
6. Overheating of internal components
7. Excessive dust or dirt blocking fans or vents
8. Outdated drivers or operating system
9. Running old versions of applications and software
10. Playing graphic-intensive video games