Coming off back-to-back second place finishes to start the season, Westwood carded five birdies in a flawless round at Doha Golf Club and shared the lead with South Africa's Anton Haig.
Sergio Garcia, Adam Scott and 2006 champion Henrik Stenson led a group of seven players who were two shots behind at 3-under 69, and there were 58 players overall at even-par or better.
Playing in the second group off the 10th tee Thursday morning, Haig set the early pace. He got as low as 6 under par before three-putting his last hole, the par-5 ninth, for his only bogey.
Westwood finished six groups later with a matching 67, posting a spotless round of five birdies and 13 pars.
A five-time Ryder Cup star and 18-time European Tour winner, Westwood is riding a hot streak that includes seven top-10 finishes in his last eight worldwide starts since the PGA Championship.
That stretch was preceded by a pair of European Tour wins earlier last season.
Westwood began this season by losing in a three-way playoff to Phil Mickelson at the HSBC Champions tournament in November. He then finished fourth at Tiger Woods' Target World Challenge in December -- an unofficial event -- before returning to the European Tour with a tie for second place at last week's Abu Dhabi Golf Championship.
The renewed success -- following three winless seasons between 2004-06 -- has left the 34-year-old Westwood brimming with confidence.
'I can't help but be confident,' he said. 'You're always a bit mindful when you have a long break, but in the middle of that long break I finished fourth in Tiger's event and last week came out and started slowly ... but got it going on Saturday and got into the tournament and had a chance on Sunday.
His second-place finishes have made Westwood the early leader on the European Tour's Order of Merit.
'I'm usually a slow starter,' he said. 'It's all to do with my fitness. I usually come out a bit lethargic and the muscles not really working, but I do a lot in the gym with the muscles on the golf swing and feel very strong and everything feels all right.'
Haig, a first-time winner at the 2007 Johnnie Walker Classic, has missed the cut in three of his first six starts this season, including two straight.
'It's all about confidence in this game -- 90 per cent in the head, that's what I was told, and I agree with that,' Haig said. 'It's a tough struggle out there, especially with the conditions like they are with the wind and there are a lot of good players out there.
'I've got a long way to go still, but I am just really looking forward to playing well again.'
The tournament lost its defending champion when Retief Goosen withdrew because of an eye problem, citing blurred vision as the result of recent corrective laser surgery.
'I'm obviously very sad that I am unable to defend my title,' stated Goosen, who hasn't won since beating Nick O'Hern by a shot last year. 'I came all this way to play, but unfortunately the eye is causing a problem.'
Paul Broadhurst, Johan Edfors, Alexander Noren and Marcel Siem joined Garcia, Scott and Goosen in the group at 3-under 69. Luke Donald and David Howell led a pack of 11 players at 70.