Bicycle acts like it's braking when I walk it
I'm assuming you have rim brakes.

Lift each wheel in turn off the ground and spin it. Does it appear to snake from side to side as it spins? If so, your wheel is out of true (it's no longer a disk but a sort of round Pringle) and it's catching against the brake pads at some part of its wobble.

If the wheels look OK when they're spinning, place the bike back on the ground and try to push the bike sideways by putting your foot against the axle. Does the wheel wobble against its mounting? If so, its bearings are bust.

Both of these are things that only an experienced bike mechanic would have the tools and skills to fix, so unless I've missed something, you're going to have to take it to a bike shop.