3 other things that will cause that.
Brake master cylinder completely full. No room for expansion as the brake system comes up to temperature.
Brakes that are not bled properly. The caliper pistons will not pull back when the pedal is released because there is air in the system.
The cure is to bleed the brakes again.
The other thing is sticking pistons. Pull the caliper, pull the pads and push the pedal while watching the pistons.
If one is hanging up, not moving out that is your problem.
Depending on the construction of the caliper, you may have to remove the outer rubber dust seal if it has one them, then wash the pistons off with chlorinated brake cleaner. Most calipers now days don't have the rubber dust covers. The ones in this video are pretty typical of ones without dust seals. If this caliper had a dust seal, you would see a rubber boot behind the pad that snapped into a grove in the piston and a groove in the caliper housing. There would be a small retainer. Remove the boot to access the piston.
Here is a video that gives you the basic idea of what I am describing.
Start by washing as much crud as you can out.
When I do it I take the pads out. Then I use a piece of metal about 1/4" thick, couple of wooden door shims back to back etc to work out the pistons that are sticky. I block the pistons that do want to move so that they can't move. This will force the stuck pistons to move when you apply pressure to the pedal.
Wash everything out good. Try it. Block the pistons that move freely to force the stuck ones to move. Wash the crud out of the stuck ones, repeat. Push the pistons back in some if you need to being careful not to damage them.
When everything is moving freely all is good. If you still don't see the pistons retract a little when you let off the pedal you have air in the system or the brake fluid has too much water in it and needs to be changed.
Chlorinated brake cleaner is nasty stuff, for this use it works far better than the non chlorinated type. Wear rubber gloves and have plenty of ventilation, as in push the bike outside. That stuff will shorten your life if your not careful and it will do it very quickly.
So beware. Don't breath it and don't get it on you or your bike. As you work the pistons out while cleaning them keep an eye on your brake fluid level so that you do not run the master-cylinder empty and pump air into the system. That would suck. If you end up adding fluid to the mastercylinder be sure to keep an eye on the level as you push the pistons back in to reassemble it or you will over flow the reservoir.
When your all done remove any fluid above the full mark on the reservoir so the brake fluid has room to expand in use.
Hope that helps.