Were mummies ever mummified alive

No. On the off chance they were alive at the start of the mummification process, they certainly wouldn't have been at the end, since the lungs, liver, stomach and intestines were removed from the body and placed in separate "canopic jars". (This practice stopped later, because it was no longer necessary due to improvements in the embalming process. However, this process would have killed anyone subjected to it as well.)