Randomization in euvm

While randomizing more than once, it is giving same data every time.
In seq_item i have written like this :-

 @UVM_DEFAULT {
	 @rand  UBit!6 paddr;
	 @rand UBit!32 pwdata;
	 ubyte  pwrite;
 }

and in sequence i am randomizing this seq_item 10 times :-
override void body(){
uvm_info(“write_seq”,“starting sequence”,UVM_MEDIUM);
req = apb_seq_item.type_id.create(get_name() ~ “.req”);
for(int i=0;i<10;++i){
wait_for_grant();
req.randomize();
req.pwrite = 1;
writeln(req.paddr);
writeln(“Inside write sequence”);
req.print();
apb_seq_item cloned = cast(apb_seq_item) req.clone;
send_request(cloned);//send_request(cloned);
}
uvm_info(“write_seq”,“Ending sequence”,UVM_MEDIUM);
}
Value of paddr and pwdata is coming same every time.