Steering wheel "center" is affected by several factors.
A severe enough difference in tire pressure can cause this symptom, but the complaint is usually that the car "pulls" (requires unusual steering wheel force to maintain a straight line on an otherwise _level_ road surface).
Tires not "matched" right to left by tread design, size and _wear_ can also exhibit a pull condition. Unmatched front to back has no effect. and it takes a greater difference of the two rear tires to cause the same amount of pull that a small difference in front tires would.
Wheel alignment would be the first check. But make _sure_ that its of the 4 wheel variety and the rear wheels are aligned to the vehicles centerline. Else the steering wheel will dynamically offset to track the off angle of the rear wheels.
Also when setting the front wheel toe the steering wheel _must_ be locked in place to its precise center. Else the vehicles alignment will be correct but the steering wheel was not included and will end up wherever.
Finally the least likely and sometimes fault is uneven tire wear. If *both* the front tires are worn cambered (vertical tilt) opposite, one negative the other positive, this then dynamically forces the steering wheel to turn until both front tires are running equally vertical. A trained eye can usually "see" if this will be a factor during an alignment. If this is a factor the only "fix" is new tires or rotate to the rear to delay the inevitable.
DIY is difficult, I've tried myself.
Simply turn both front tires the same direction that the steering wheel is offset by loosening the front toe adjusters. Increase the length of one tie rod to "turn" the tire inward and decrease the other the identical amount to "turn" it outward.
E.g. if the steering wheel is offset to the right then the right tire needs to turn right (shorten the tie rod length) as with the left tire (lengthen the tie rod) so that when the steering wheel is turned back to center (left) the front tires are now straight.
Estimating the amount is one difficulty that can only be mastered by experience. And this "trick" assumes that the fault is due to an incorrectly centered steering wheel from an earlier alignment. You will mask one symptom of a rear tire out of alignment condition.
Too many oopses and the error factor creeps in. You'll throw the alignment out of spec resulting in abnormally rapid tire edge wear (inner or outer depending on which direction you oopsed) and especially on the Insight a noticeable and measurable loss in MPG. Incorrect toe causes increased tire drag hence the edge wear. Not to be confused with _both_ edges of each tire wearing. Which is one symptom of the Insight and the OEM Bridgestone tires. Apparently an oversight and something to do with their low rolling resistance design.
HTH!
