I got do some test by myself. I found out the problem of freeze probably cause by the app "supportassist" and "dell power manager". I didn't test which got problem but I just uninstall both software. And problem solved. my laptop not so lag and the freeze problem not happening again even I add in my new ssd in. So, maybe follow this can help you.  [URL]#M3882 
My laptop will freeze randomly.  Like I was listening music, (At that time I also doing something else)  it will just stop will the last sound and keep continue it for few seconds. and my screen will freeze at the same time.  All key is not responding, and I cover my lid, my screen still on.  I only can do is force shut down.  previously I saw a post that change power option sleep to never, I had done that and also change my battery settings to "primarily AC use"  [URL]#M26910 However, it still happen.  I am not sure is it my new ssd causing problem (cause the first time happen before I put in and before change the power option) (after change the power option, there 2-3 days nothing happen)( My new ssd : SA2000M8/500G-Kingston 500GB A2000 M.2 2280 NVMe) Can somebody please help me ,I really scare it freeze while I taking exam. 
Inspiron 7501 system freezing and only can force shut down