Pilot reported while in cruise flight being vectored for traffic in IMC conditions and the vectors placed the two aircraft on a collision course resulting in the pilot taking evasive action to avoid a collision with the other aircraft.

Narrative

I filed for a IFR flight plan from ZZZ to GRI. I departed ZZZ at approximately XA:25 with myself and two passengers. Fort Worth Center was vectoring me around a storm which had me crossing over Shepard AFB (SPS). I got handed over to Shepard Control and I crossed over SPS being vectored by Shepard Control in 100% IMC conditions on approximately a 310 degree heading. Not sure the distance North West of SPS that I was when Shepard Approach told me to turn to a 270 heading for traffic. I acknowledged and turned to 270. At this time I noticed another object North West of me on an approximate heading of 180 and 400' above me (I don't remember distance at the time). This put me on a course to cross the path of that plane. I asked approach if it would be better if I turned to a heading of 360; direct destination. At the time this would of put me to my right of the plane North West of me on a 180 course. After some time passed Shepard Approach told me to turn to 360. I acknowledged and turned to 360. I observed that I was heading for the plane on the 180 heading. I don't remember distance but Foreflight showed them at 400' above me. I was expecting Shepard to adjust my heading or altitude or the other airplanes for avoidance. This did not happen.The next transmission I received from Sheppard Approach was that I was about to 'MERGE' with the other plane. I heard the Garmin say traffic 1 mile. I took immediate evasive action and went into an immediate right turning decent. As I was in the right turn there was what felt to be some type of disturbance to the plane that pushed me more right and tried to roll the plane to the right. Not sure if this was from the weather I was in or the other plane.At 6000' I leveled the wings and stopped the dive. I then started to climb back up to the assigned 8000' level. Shepard approach contacted me and I responded that I was returning back to the 8000' level. We were in 100% IMC with no visibility. I never once heard a transmission from the other plane or Shepard approach to the other plane. I do not know what the other plane was.