Quick answer
Because the problem disappears while driving, the fault often shows most clearly at low rpm when engine movement and idle smoothness matter most.
Many causes are fixable without major engine work.
Is it serious?
Often minor
Especially if performance is normal.
Monitor worsening
If vibration increases, inspect soon.
Warning lights?
Needs faster diagnosis.
Noise present?
Mount or accessory issue possible.
Rough idle only
Often manageable initially.
Persistent issue
Do not ignore for months.
Common causes
- 1Worn engine mounts
- 2Dirty throttle body
- 3Minor ignition misfire
- 4Vacuum leak
- 5Low idle speed control issue
What to check next
Notice whether vibration changes with air conditioning on, in gear, or when cold versus warm. Those clues help diagnosis.
A diagnostic scan and visual inspection are often worthwhile.