Started having some trouble with my ol' reliable TD5 defender. It started to shake vigorously when I first start it up, if its the first or second time I start it up is shakes for a few seconds then dies (unless I give it some gas then it goes back to normal). After the engine warms up a bit it stops dying but it still shakes excessively for 2-3 seconds before going to a normal idle.

I was thinking it may be the glow plugs but wanted to get more experienced opinions before I start throwing parts at it.

Glow plugs would be second check after fuel filter

When the TD5 starts up, it typically only fires on the front 4 cylinders for a moment or two. This is controlled by the ECU. The rearmost cylinder has no glow plug and the ECU doesn't activate its injector for a few seconds after starting. You can sometimes feel the engine being a bit sluggish before all 5 kick in.

As well as checking the glow plugs I wonder if there's some sort of fuel delivery problem? For example after I've serviced mine and changed the fuel filter I go through the purge sequence a couple of times and run it and everything's fine. Then the following day it can be reluctant to start and runs rough for a few moments when it does start. I put this down to some residual air accumulating in the cylinder head, which is the highest place in the fuel circuit. So maybe your fuel is tending to drain back into the tank while it's standing. There's supposed to be a little rubber gland in the fuel filter housing to stop this happening but it doesn't last for ever. Or air may be finding its way in via one of the pipe joints near the cylinder head.

Where is the fuel filter located? Als do you happen to have a picture, or part number of the rubber piece you mentioned?

The fuel filter and its housing are in the rear wheel arch on the driver's side (RHD vehicles), just in front of the wheel.

There's a post her which describes the relevant items:
https://www.landyzone.co.uk/land-rover/td5-fuel-issues-starting-issues-fix.319376/
And there's more discussion here:
https://www.landyzone.co.uk/land-ro...starting-and-the-little-orange-chappy.296215/
The problem lies with the little orange bladder valve which Land Rover do not appear to sell separately.

Brown said:

The rearmost cylinder has no glow plug and the ECU doesn't activate its injector for a few seconds after starting.

Click to expand...

Really?

Brown said:

The problem lies with the little orange bladder valve which Land Rover do not appear to sell separately.

Click to expand...

They can be got from a guy in OZ.

Cheers

Where the glow plug would go on the rearmost cylinder, the space is taken up by the fuel pressure regulator, so you only get them on the first four cylinders.
Re: not firing on all 5 cylinders at start up, CharlesY and Sierrafery say this, so I took it in good faith.
e.g. https://www.landyzone.co.uk/land-rover/td5-cold-start-issues.92129/

Check the engine mounts

UPDATE: I replaced the glow plugs and the fuel filter. While I had the intake manifold off I cleaned out a LOT of clumped up oil from inside the throttle body and the intake manifold. The defender is still having trouble when it first starts up. I would almost say that it has gotten slightly worse. I also notice that now the exhaust is spewing out quite a bit of oil. Could this also be a symptom of my initial problem?