Start with observation and reversible checks before replacing hardware or resetting the system.
Describe when the slowdown occurs
Notice whether the problem appears at startup, in one application, during downloads or after the machine becomes warm. The pattern narrows the cause.
Check simple constraints
Restart, confirm available storage, review active processes and install trusted updates. Scan for unwanted software and check whether a failing drive or high temperature is being reported.
Change one thing at a time
Create a backup before repairs, record what you change and test after each step. A complete reset should be a later option, not the first response to an unexplained symptom.