I'm playing Telemann's Concerto in G Major for Two Violas (top line) and I'm having problems with crossing strings while holding down on fingerings (4 fingers on d, 3 on a for example). I find this restricting to my hands and it eventually burns a lot (i normally burn but this gets extreme at some points).

Does anyone have input or pointers on how to overcome this?

What strings are you using? Gut or Nylon would be lower tension so less stress on the hand. If you can, try playing in 3rd position to use 1st & 2nd position. Check the action (height of strings). If you have a cheap instrument then the action may well be too high.

Disclaimer, I am an amateur and I can only say what works for me. If I was having problems like this, I would find a teacher forthwith if not fifthwith and get your technique looked at. If it hurts like this then your body is trying to tell you something. It may also be smart to see a doctor and check that the fault doesn't lie somewhere else if you know what I mean!