Garage door frame slumping.
It would be helpful to know where you are located, in terms of roof loading. Near as I can tell, you have a 10 foot long double 2x10 header, possibly with a piece of 1/2 inch plywood sandwiched between the 2x10's. This appears to be supporting only the roof, as I did not see any indication that there is storage being supported by the rafters.
I took a quick crack at some computations. I assumed the garage was 20 feet deep, you can confirm this. Using 40 psf roof load (heavy load based on snow, but then you never told us where you live) plus 10 psf dead load (no storage, framing load only) makes for 50 psf total. Assuming your header picks up half the load of the roof, that makes for 500 pounds/foot distributed load on the header.
Even at that load, which may be high (depends where you are located), the beam is probably structurally adequate (it is close). However, the deflection at midpoint would be a little less than half an inch, which should not be too noticeable. And the deflection would only occur if you got a major snowload condition.
To make more progress, you need to verify ALL the dimensions discussed, and tell us where you live.