UE 4 crash

Everything was working fine since one month but today suddenly UE4 is crashing and i am getting this error suddenly.

LoginId:5d9484314521e07ad5fd69960d13df71
EpicAccountId:ae7f93e6c8ef4b289fc3a2d911ea3738

Assertion failed: [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11Util.cpp] [Line: 198] Unreal Engine is exiting due to D3D device being lost. (Error: 0x887A0006 - ‘HUNG’)

UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_D3D11RHI
UE4Editor_D3D11RHI
UE4Editor_D3D11RHI
UE4Editor_D3D11RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_SlateRHIRenderer
UE4Editor_SlateRHIRenderer
UE4Editor_Core
UE4Editor_Core
UE4Editor_RenderCore
UE4Editor_RenderCore
UE4Editor_Core
UE4Editor_Core
kernel32
ntdll