Any unusual shaking or vibrating forces coming from the engine is cause for concern. It could be something as simple as old spark plugs producing an uneven power delivery, it could be something serious like worn or broken engine mounts, or it could be even more serious in the case of internal engine damage.
Common reasons for this to happen:
Most often, one of the following components is at fault:
Old and worn spark plugs and wires (most commonly the issue)
Loose or disconnected hoses on and around the engine (not the coolant hoses that go to and from the radiator) are frequently culprits behind intermittent engine operation.
Loose connections at the positive and negative battery terminals
Very dirty or clogged air filters can also cause your engine to underperform.
Loose timing belts are another likely cause. A mechanic will check these and replace them if they appear loose and worn. To check for engine-mount problems, the mechanic may try shifting from "neutral" to "drive" and back, while the engine is running. If the vibrations disappear or reduce dramatically in "neutral," it’s likely that you need new engine mounts.
What to expect:
A top-rated mobile mechanic will come to your home or office to determine the source and cause of the shaky engine, and will then provide a detailed inspection report that includes the scope and cost of the necessary repairs.
How important is this service?
Given the range of the severity of potential issues, from faulty spark plugs to weak motor mounts, it's important to have a mechanic provide a thorough inspection as soon as possible.