2010 VW Caddy 2.0 SDI

A couple concerns which may or may not be related.

Starting: When I first got the van nearly three years ago it started first turn of the key. Past few months, it has to be cranked for longer. Sometimes it doesn't start at the first attempt but has never not started at the second try. Also, sometimes when turning over it sounds like it is trying to fire on three cylinders with that 'digadigadiga' noise, but this has never been the case when it is running.

Losing power: A few weeks ago while driving along on a steady throttle in 5th gear at about 50mph, it abruptly seemed to lose power and revs, almost like my foot had slipped off the throttle (the engine didn't cut out). I dipped the clutch and blipped the throttle, it revved fine, so I let the clutch back out and it was driving as normal. Only happened the once till today when it happened three times, twice on one journey about 15 minutes apart, then once again a couple of hours later (on the 45 minute drive home, it was fine)

With regards for the starting, the van was in the garage having this investigated, but the mechanic couldn't find anything amiss. I had been worried it could be the injectors, but the mechanic said he checked them and they seem to be working fine (don't know what this involves, or if the check is accurate). Although he didn't change them (misunderstanding on my part), he suggest maybe the glow plugs. I completely forgot to mention that one instance (at the time) of losing power, so not sure what his take on that would be.

Any suggestions?

Thanks!