Crank acceleration makes sense.
Try unplugging the temp sensor and see if the glows stay on longer and if you can start easier. Could be a bad sensor. You can also test the glows and wiring harness to make sure they're alright. Should be instructions and numbers for those on TDIClub.
Also, make sure to check the basics of your battery, alternator, and starter. Our TDI was really hard to start for awhile and it got worse the colder it was. Turned out it was a dying starter. The new one fixed everything.