I have a Keeprite NTC6075FBG1 that's about 8years old,It starts up ventor motor first then the burner lights then the blower motor start,after a few minutes of being on blowing heat the burner goes out, nothing else stop just the burner goes out, then about 45 second later the buner relights and blows hot air, this happens about 3 or 4 times during the call for heat.

First thing I would check is if there is a limit stat opening and shutting the burner off. There are plenty of variables here and your description doesn't give me enough to eliminate others, but start with either a faulty limit stat or incorrect air flow. Beyond that I recommend a professional, there are just too many things that it could be to list here not to mention describing the testing methods.