I've been offered a short notice interview todaywith a 20 minute presentation for Friday. Applying for this job was a shot in the dark and felt confident of doing the job upon applying. On reflection now having accepted the interview I am having second thoughts, not about the job just lack of time to prepare and lack of experience in the field in which the role has been advertised. I don't want to burn bridges here as its internal posting but I want to decline. How can I put this across without sounding flakey!?