Having enigne and brake problems

I was hoping to get a little help in diagnosing a problem in
my 2005 kia spectra. Im stumped at the moment because
it will run fine for about 4 or 5 miles once the engine gets
warmed up it doesnt seem to lose power more like the
brakes get stuck engaged an it doesnt want to go. Again
thats why im stumped. If someone has had this issue or
knows what i can do to get this problem fixed an can give
me pointers its greatly appreciated. Money is tight an need
to get back am forth from work.