Hello there @harshil_kansara1!
Checking around the UE community, and considering you have already adjusted both scalability and LOD settings, the most likely cultrip for this scenario would be texture streaming.
Find the textures associated to your custom character, open them in editor, and check under Texture > Texture Streaming, then see that Never Stream is not checked. As well, ensure that LOD Bias is set to 0. Finally, confirm if Virtual Texture Streaming is checked on these textures.
For further options to test, like adjusting the texture pool, please follow the community guide below: