The GPU load can fluctuate between 50% and 100% due to LHR (Lite Hash Rate) unlock method. This will happen on most LHR GPUs where LHR parameter is used. Some miners like LolMiner might automatically apply LHR unlock without any Extra Launch Parameters.
Fluctuations are expected and it means that LHR unlock is working.
List of potential LHR graphic cards:
NOTE: Nvidia removed the LHR limiter in drivers 522.25 and newer.