The latch is probably sticking when you turn the handle. Combined with a misalignment of the latch and the striker plate, that causes the latch to not fully center in the hole in the striker plate.

Moving the striker plate is the solution. Loosening/tightening the two bolds that hold the two sides of the door handle together should solve the sticking part.

When the weather changes, frames can warp temporarily and cause alignment problems between the bolt and the hole it goes into in the strike plate. This is very common. It sounds to me like the spring-loaded bolt only goes in a fraction of an inch because there is friction between the bolt and the hole, then it can later pop open with a breeze or some vibration. In any case moving the striker plate or enlarging the hole a bit in the right place should resolve this. (The bolt could be a hair high, low, or too far out from the jamb). However, it sounds to me like you aren't very handy, so it would make sense to get someone more knowledgeable than you to fix this so it gets resolved correctly without messing anything up. Bottomline: you don't need a new door or a new deadbolt...just a simple fiddling around by someone who understands where to make a slight modification.

If this is a door that connects between the house and the garage I'm assuming that it is self closing. What I notice is because of temperature changes, etc. they seem to slam in the summer and not want to close completely in the winter. So you have to strike a balance between closing firmly without slamming. If it's self closing you should look at the hinges for holes. Some doors are just one hinge and some doors have adjustments on all three hinges. You usually have to hold it with a hex wrench and reposition the pin. Google till you find your particular hinge and follow instructions. Then adjust till it closes firmly but doesn't slam.

Might be a bit late to chime in on this, but will do so anyways. One thing that some people might over look is that with a steel door is the weight. With a lot of use the door could be sagging a bit and to correct that see about tightening the hinge screws. Other than that check the gap between the door and frame. The standard residential latch is 1/2"-5/8". Through use sometimes the latch plate will round off on the edge and could be used to replaced. The home stores have this for less than $5.

"With a lot of use the door could be sagging a bit and to correct that see about tightening the hinge screws."

If the screws are the ones that cam with the hinges (often barely over an inch long) they do not even reach into the framing outside the door jamb.

Tightening them may help temporarily, but replacing at least one screw on each hinge with something at least 2 inches long is a better long term fix.