You've set the RCIE bit, which enables interrupts for the USART receive path.
But there is no interrupt handler for that interrupt source.

After it receives any data, it will jump to the ISR, which does not handle the interrupt, and does not clear the flag.
So as soon as it exits the ISR, it generates another interrupt because the RCIF flag is still set.

This continues for about 2 seconds until the Watch Dog Timer resets the PIC.

When you are handling the USART receive in the Main loop ... don't set the RCIE bit.