noisy electric oven?

i have a baumatic pt2815ss 90cm twin electric oven,i have had it stored in my house about 3 years since i bought it new,i had it installed last week and when i used it today after about 20 minutes on full power with the fan function there is a loud rattling noise coming from the oven,when i turned the oven off i could see that the fan stopped but the noise continued,after at least 20 minutes the cooker was still making the loud noise so i turned it off at the mains and waited about an hour and turned the power back on and the noise has stopped,any thought?