  In the magic angle twisted bilayer graphene (MATBG), non-Fermi liquid like
transport phenomena are universally observed. To understand their origin, we
perform the self-consistent analysis of the self-energy due to SU(4) valley +
spin fluctuations induced by the electron-electron correlation. In the SU(4)
fluctuation mechanism, the fifteen channels of fluctuations contribute
additively to the self-energy. Therefore, the SU(4) fluctuation mechanism gives
much higher electrical resistance than the spin fluctuation mechanism. By the
same reason, SU(4) fluctuations of intermediate strength provide $T$-linear
resistivity down to $\sim1$K. Interestingly, the $T$-linear resistivity is
robustly realizedfor wide range of electron filling, even away from the
van-Hove filling. This study provides a strong evidence for the importance of
electron-electron correlation in MATBG.
