Volvo CX90 Starting problems after air compressor repair....What?

To get to the air compressor for replacement, the mechanic went down through the top instead of going underneath due to a plate welded under the car. He had to remove lots of parts to get to the compressor. Now when I start the car, there is a weird vibration and the car won’t start. This occurs intermittently. I think something he removed is not replaced correctly or tight enough. Is this possible? What does this sound like to you?

I think your mechanic may not be the mechanic that he thinks he is. Time to return the Volvo to the shop. Replacing an air compressor is not rocket science.

Yes I think mechanic did something wrong.

Any Check Engine Light on? Is the vibration present at idle and at speed both? Any noises?
Are you saying the car is currently disabled and will not start at all?

There’s not enough info known to be able to even guess wildly at the cause.

“There’s not enough info known to be able to even guess wildly at the cause.”

True enough but the person that caused the problem is glaringly obvious.

Any mechanic worth his salt will stand behind his work. Go back and let him take a second look. If it were me I’d want you to bring it back so I could fix the problem. For no additional charge, of course, unless it turned out unrelated to the work I’d done.