Default [Q] [HELP] Bootlooped i9500, cant access download mode

Hey there everyone, and thank you all in advance for any help i might receive with my issue. I have a S4 gt-i9500, i havent played around with rooting or installing any custom firmwares so as not to void my warranty, but today, out of the blue my phone just turned off and started an incessant bootloop. I cant even get it to stay off, when i try to access recovery mode i get this little pic that goes by so fast i cant really see it, but it looks like the android dummy lying down dead , with a red exclamation mark on top of it. I can access the first stage of download mode, but when i press Vol up, nothing happens and after a few secs the bootloop starts again(even if i dont press anything). I took my phone to my provider and they told me my warranty was violated because of some bs key scratches on the chrome bezel, id really appreciate any info on how to make it stay in download mode long enough to flash a rom or custom recovery on it to see if i can get it fixed.